Version 1: 31 March 06,   Version 2: 6 May 06, Version 3: 18 Oct 2007, Version 4: 18 November 2007, Version 5: 21 Mar 2008

From a passionate Kenwood TS-950SDX owner. The 950SDX is proclaimed by many as one of the greatest transceivers ever produced.     

This page is provided because:

·Some information here is not available anywhere else and should be useful to any TS-950 owner,

·Information does not exist in a single web site which is easy to follow,

·If the information remains available more TS-950s will be repaired and functional, (and probably improved),


The intention is to acknowledge the person who discover the information so questions can be sent to that person.

When information is already well documented and reliably maintained on another site then a hyperlink is made to that site to avoid yet another slightly different version.

I will publish all email feedback at the end of the page, so that whatever is discovered by others can be shared by all. Please email to

Yours sincerely

Jeff King ZL4AI  /  DU7

Disclaimer: No liability or responsibility whatsoever is taken for any of the information on this site. You assume total liability for any modification you undertake.
Copyright: Everything on this page 









Raspy Audio Distortion.. 9

Raspy Audio sequel took a second repair: 22

The Return of Raspy Audio: Third Repair. 22

VCO 2 Problem.. 25


Battery Replacement.. 28

Jumping Frequencies all  by Itself: Solution still Required.. 35


Preventing Final FETs failure. 38

Using multi meter to check if finals are ok?. 39


Not recommended practice / This is the wrong way to set up finals. 41


The terrible no volume 50 hertz audio hum. That drove me nuts. 43


1.8 Khz filter PROBLEM ???. 46

RM-1 Controller required for full control. 47

Service Menu Warning. 48

Part of DSP Circuit is missing. 49


[Kenwood] TS950SDX filters. 50

How I gave new ears to my TS-950sdx.. 51

TS-950SD general coverage transmit mod (1.8-30MHz Continuous TX) 57

Power On Funktions. 59

Allows sub-receiver to be on different band than Main receiver. 59



Preventing final FETs failure. 64

Front-panel Sidetone Level Control for theKenwood TS-950S (may also apply to TS-950SDX) 64




RFI Susceptibility.. 67



Audio Modifications. 68







Swift performance and surgical precision are second nature to the TS-950SDX. Quality engineering blends aesthetic simplicity of form with a wide range of advanced features -- such as the built-in DSP (digital signal processor) and MOS FET final section. The result is exceptional transmission signal purity and first-class audio quality -- a benchmark for HF communications. And operating ease is just as impressive, thanks to the convenient menu system and many other user-friendly refinements.

Features at a glance:

160 m ~ 10 m amateur band operation

100 kHz ~ 30 MHz general coverage receiver

Built-in DSP (Digital Signal Processing)

Digital AF filters

MOS-type FET final section

Dual-frequency receive

SSB IF slope tuning

Menu system

Automatic antenna tuner

AIP system

100 memory channels

Built-in AC power supply

TS-950SDX in detail:

Digital signal processor (DSP)
The digital accuracy and reliability offered by the built-in DSP, for both TX and RX, translate into an unprecedented advantage in HF communications.

  • Outstanding performance
    Carrier suppression is more than 50 dB, and unwanted-sideband suppression is also greater than 50 dB.
  • Digital AF filters
    15 LPFs for SSB and CW modes (with cutoff frequencies ranging from 600 Hz to 6 kHz), and 3 BPFs for FSK use (with a central frequency of 2200 Hz) are menu-selectable.
  • Digital filtering eliminates key clicks
  • Superior FSK transmission circuit
    The data control oscillator provides rapid switching for the cleanest FSK signal. The operator can choose 170, 200, 425 or 850 Hz FSK shift.
  • Selectable sound quality
    To ensure high-quality sound, there are 4 low-cut filters plus a through position, and 4 high-cut filters.

Dedicated Power MOS FET (MRF 150MP) final section
The TS-950SDX was the first amateur radio transceiver to feature an FET final section. Excellent linearity results in greatly improved transmitter performance and enhanced reliability.

Dual-frequency receive capability
For maximum convenience when operating split frequencies, the TS-950SDX can simultaneously receive two frequencies, which can be within 1 MHz of each other.

  • Independent IF & AF circuits for main & sub receivers
  • M/S (main/sub) select for operating sub receiver with main tuning knob
  • TF-SET (transmit frequency set) and "delta" F function
  • Independent CW filter (500 Hz) and S meter for sub receiver
  • Simultaneous, independent monitoring
  • Using an external speaker or headphones, main and sub receivers can be monitored simultaneously yet independently; monaural and mixed monitoring are also available.

Powerful menu system
Rapid, user-friendly access to the many features and functions of the TS-950SDX is provided by the menu system. This includes 32 menus for power-on settings, and a further 29 menus for use during transceiver operation.

Quick Memory
The Quick Memory feature allows for stacking and recalling frequency, mode and filter information on the fly. The 5 channels reserved for this purpose are independent of main memory.

Automatic antenna tuner
Built into the TS-950SDX, for maximum operator convenience, is a completely automatic antenna tuner (compatible with impedances of between 20 and 150 ohms), controlled by a microprocessor preprogrammed to rapidly tune for minimum SWR.

First-rate receiver performance and sensitivity

  • Superb frequency stability
    A TCXO (temperature-compensated crystal oscillator) and microprocessor-controlled digital PLL, DDS circuits control the frequency in 1 Hz steps. Consequently, the reference frequency (20 MHz) is accurate to within ±0.5 ppm between -10 degrees and +50 degrees C.
  • AIP system
    AIP (Advanced Intercept Point) is an exclusive circuit design that provides superior dynamic range (when AIP is selected). The use of two selective RF amplifiers results in a significantly reduced noise floor level.
  • 15 band-pass filters
    The RF amplifier section and 15 band-pass filters -- including 10 BPFs for amateur bands -- together offer outstanding two-signal characteristics.
  • Selectable IF filters with memory

Innovative interference reduction

  • SSB IF slope tuning
    For LSB and USB modes, independent high-cut and low-cut controls permit the operator to select the ideal IF passband width quickly and easily.
    With the variable-bandwidth tuning control, passband width can be adjusted without affecting the centre frequency. In CW, FSK and AM modes, the IF VBT control allows the operator to avoid interfering signals while maintaining optimal signal-to-noise ratio.
  • High-precision IF notch filter
    Available for all modes except FM, the tunable IF notch filter provides approximately 45 dB of attenuation in a very narrow frequency range.
  • Dual-mode noise blanker plus noise-select function
    The blanker offers two modes -- NB-1 ("pulse") and NB-2 (longer duration noise) -- and can be tailored to match specific noise and signal level conditions. Also, by dedicating the sub receiver to noise detection and using its blanking pulse to blank the main receiver, the operator can soon determine the optimum setting.

High-performance CW functions

  • Full break-in and semi break-in
  • Reverse mode
    In reverse mode the pitch of interference competing with the CW signal is reversed, so the operator can approach the target from either side.
  • Variable pitch control
    Using the pitch control, CW pitch frequency can be varied between 400 Hz and 1000 Hz in 20 Hz steps. Current pitch frequency can be checked using the menu system.

100 memory channels
The TS-950SDX is equipped with channels 0-89 for independent storing of transmit and receive parameters such as frequency, mode, filter setting, auto-tuner and tone frequency. Memory channels 90-99 can be used to establish the upper and lower limits for the programmable band marker.

Versatile scanning
Any or all of the memory channels may be scanned, with selected channels skipped using the programmable memory channel lock-out function. The TS-950SDX can scan up to 10 groups automatically within the limits specified by the programmable band marker, and can also scan sub-receive frequencies. Scan speed can be varied continuously using the RIT/XIT control.

Other Features:

10 direct band access keys

Dual digital VFOs with A=B key

Multi-function display and digital bar meter

Ultra-fine (1 Hz) tuning with Direct Digital Synthesizer (DDS)

4-step (0, 6, 12, or 18 dB) RF attenuator

Switchable AGC circuit (OFF/AUTO/SLOW/MID/FAST)

All-mode squelch circuit

RM-1 remote function keypad (supplied)

All-mode data communications

Optional IF-232C interface for computer control

All-mode RF output power control

Built-in AC power supply

Dimensions (W x H x D)

402 x 141 x 400 mm (15.83 x 5.55 x 15.75 in.)











The TS-940 page

has the following which is equally relevant to the TS-950:


-Sources of parts,

-Links to useful sites, including manufactures, and containing Kenwood TS-950, TS-940 + TS-930 information

-Identifying when the radio manufactured [from serial number, establish date and unit number of productions that month]










Available at:


ASB1016.JPG                 TS-950 Hum With Monitor On S/N 1060XXX                                           55.06 KB


ASB1017A.JPG             TS-950 Noise When NB1 On For Sub Receiver                                        48.23 KB

ASB1017B.JPG              TS-950 Noise When NB1 On For Sub Receiver                                        39.03 KB


ASB1018A.JPG             TS-950 14.200 Mhz Transmit Spur S/N 1010XXX                                     63.92 KB

ASB1018B.JPG              TS-950 14.200 Mhz Transmit Spur S/N 1010XXX                                     41.38 KB


ASB1019.JPG                 TS-950 Low Power Output After Temperature Protect                            63.72 KB


ASB1020.JPG                 TS-950 Infinite SWR At Beginning Of Transmission                               62.99 KB


ASB1021.JPG                 TS-950 Smoke From Antenna Tuner                                                           54.63 KB


ASB0990A.JPG             TS-950 Final Amp.Bias Circuit Change                                                       84.81 KB


ASB0991.JPG                 TS-950 Rear Cooling Fan/Power Down                                                      60.30 KB


ASB0959A.JPG             TS-950SD Speech Processor Noise                                                             83.41 KB

ASB0959B.JPG              TS-950SD Speech Processor Noise                                                             29.23 KB

ASB0959C.JPG              TS-950SD Speech Processor Noise                                                             49.95 KB


ASB0960.JPG                 TS-950SD Low VS-2 Audio                                                                          78.79 KB


ASB0961.JPG                 TS-950SD N.B. Gate Switching Noise                                                         72.23 KB


ASB0962A.JPG             TS-950SD RX-TX Switching Time With Amp                      81.11 KB

ASB0962B.JPG              TS-950SD RX-TX Switching Time With Amp                      33.25 KB


ASB0963A.JPG             TS-950SD RX Noise On 10 & 15 Meters                                                    74.17 KB

ASB0963B.JPG              TS-950SD RX Noise On 10 & 15 Meters                                                    61.74 KB


ASB0964A.JPG             TS-950SD Two Second TX Delay With Moni Switch On                       75.60 KB

ASB0964B.JPG              TS-950SD Two Second TX Delay With Moni Switch On                       31.57 KB


ASB0971A.JPG             TS-950SD Receiver Noise With Volume At Minimum                             60.77 KB

ASB0971B.JPG              TS-950SD Receiver Noise With Volume At Minimum                             29.63 KB


ASB0982A.JPG             TS-950SD TX Image On 18.115 MHz Causing Distortion   73.24 KB

ASB0982B.JPG              TS-950SD TX Image On 18.115 MHz Causing Distortion   48.49 KB


ASB0984A.JPG             TS-950SD 80 Meter Spurious Emmision On 80 Meters                            73.46 KB

ASB0984B.JPG              TS-950SD 80 Meter Spurious Emmision On 80 Meters                            46.42 KB


ASB1024A.JPG             TS-950SD Transmit Spurs                                                                             62.49 KB

ASB1024B.JPG              TS-950SD Transmit Spurs                                                                             53.20 KB


ASB1052.JPG                 TS-950SD Spur on 18.115 MHz                                                                    72.75 KB




ASB0998A.JPG             TS-950SDX Random Transmit When Mode Is Changed    64.61 KB

ASB0998B.JPG              TS-950SDX Random Transmit When Mode Is Changed    34.13 KB


ASB0999A.JPG             TS-950SDX No Beep In Headphone When Using Mono Phones         68.53 KB

ASB0999B.JPG              TS-950SDX No Beep In Headphone When Using Mono Phones         44.45 KB



ASB1001A.JPG             TS-950SDX Distorted DRU-2 Transmit Audio                                          61.62 KB

ASB1001B.JPG              TS-950SDX Distorted DRU-2 Transmit Audio                                          34.31 KB


ASB1003A.JPG             TS-950SDX K1EA Ver.8 Program Problems - New Eprom   76.80 KB

ASB1003B.JPG              TS-950SDX K1EA Ver.8 Program Problems - New Eprom   54.25 KB


ASB1007.JPG                 TS-950SDX Speech Processor Adj/Excessive Noise                               63.88 KB


ASB1009.JPG                 TS-950SDX 3rd Order Imd Improvements                                                  53.36 KB

ASB1009A.JPG             TS-950SDX 3rd Order Imd Improvements                                                  62.17 KB


ASB1012.JPG                 TS-950SDX Key Click With Bug Type Key                                               50.74 KB


ASB1026A.JPG             TS-950SDX Click Noise When Notch Is On                                              73.35 KB

ASB1026B.JPG              TS-950SDX Click Noise When Notch Is On                                              54.08 KB


ASB1043.JPG                 TS-950SDX Installation Of YG-455S1                                                         68.64 KB


ASB1045.JPG                 TS-950SDX No Vfo B After Split Operation/Micro Change                    64.45 KB


ASB1047A.JPG             TS-950SDX Carrier Point Adjustment                                                         75.49 KB

ASB1047B.JPG              TS-950SDX Carrier Point Adjustment                                                         82.27 KB

ASB1047C.JPG              TS-950SDX Carrier Point Adjustment                                                         59.18 KB


ASB1050A.JPG             TS-950SDX Sub Band Residual Noise                                                        73.66 KB

ASB1050B.JPG              TS-950SDX Sub Band Residual Noise                                                        47.28 KB


ASB1053.JPG                 TS-950SDX Change Of Final Gate Resistor Type                                     76.53 KB


ASB0989A.JPG                     DRU-2 Erratic Playback/Memory Loss P.1                                      64.61 KB

ASB0989B.JPG                     DRU-2 Erratic Playback/Memory Loss P.2                                      34.65 KB




 ZL4AI found some of the diagrams Kenwood put on the web cannot be read. Legible versions can be obtained by emailing Kenwood. It helps to point out there is considerable Health and Safety issue / liability fro Kenwood if an Amateur using information makes a mistake because the information Kenwood provided could not be correctly interpreted.







These can be found from time to time on the internet. If you need a service manual, we offer it on a comprehensive CD-ROM, which contains in PDF format:


- Service Bulletins (above)

-TS-950S and SD service manual,

-TS-950SDX service manual,

-TS-950SDX operators manual,

-TS-950SDX promotional brochure (in full colour),

-MC-90 operators manual


If you require the CD cost is $US10.00 plus postage. Please to request delivery.









This is the main reason for preparing this page. So useful repair information not easily available is in one place.



  Raspy Audio Distortion

 Symptoms experienced by ZL4AI

 - When using an amp [SB201] started getting very distorted scratchy transmit audio.

- Turn 950sdx off. Leave say 20 minutes. Turn on and noise usually gone, for another 10 minutes of transmission.

-Did not use the 950sdx much for 3 months.

-With different amp [SB221] the same distorted transmit audio.

- Processor meter reading completed disappeared. Processor seems to work OK , but regardless of where you turn the control nothing shows on the meter. Cant seem to bring back the processor reading

If just use the radio alone then the transmit audio appears OK.

-Then after a couple of more weeks received audio becomes very distorted and lower level.

-Turn radio off for 10 minutes and received audio is OK.

- Distorted audio tends to occur first at top of band: E.g. Distorted at say 14315 but tune down to sat 14180 and no distortion. Leave 950 running and distortion audio moves down band to 14180.



ZL4AI suspected the faults could be one of:

- Kenwood published fix of reordering the connections to CP1, CP2, CP3 and CP4 on the PLL board, or


-Amateur service bulletin 1007: Reports of low: comp meter sensitivity, or noise on the transmitted audio when using the speech processor is normally a result of mis adjustment of the proc in control. The control is very sensitive and is difficult to adjust properly.


Further inspection showed that ASB 1007 had already been completed.




ZL4AI found the following advice on the Kenwood Archives:


[Kenwood] TS950SDX Distorted TX audio 

John Tait

Wed, 6 Nov 200200:36:46 -0000


Awhile ago, I post a request for help with a problem on a TS950SDX. It had intermittent distortion on the "Moni" audio, 
and also occasionally on the TX audio. Unfortunately, nobody came up with a solution..
       Anyway, I sent it off to the "premier??" repair shop in the UK.. It was returned, unrepaired, with a note saying
  "this a common problem with 950s, there's no real cure for it"..    Eh??
    Class A1 certified nonsense..!!
I once more turned to the web for help... Lo and behold..... On searching for inspiration...There it 
was..under "Countermeasures against cold solder joint at resistor block CP1-CP4 in PLL unit" the exact symptoms,
AND the cure thrown in for good measure..!
  We're now up and running perfectly again..
           THANK YOU
John  EI7BA




[Kenwood] TS950SDX, distorted xmit and rcv

Draper, Bruce L
Thu, 25 Sep 2003 13:09:12 -0600

Six months ago, my TS950SDX would have distorted signals, only on transmit, only with the internal tuner in line, and only 
after being on the air for a half hour or so. Three months ago, it also started happening when NOT using the internal 
tuner. Now the raspy signals are also on receive. Seems to be all bands, all modes, although I haven't done an exhaustive 
Is this a known problem with a straightforward fix? If not, where's the best repair center?
      Bruce, AA5B


[Kenwood] TS950SDX, distorted xmit and rcv

John Tait

Thu, 25 Sep 2003 21:25:26 +0100

Hi Bruce ..
       Go to
Then to Kenwood..... 950... and look for the bulletin  "Countermeasure against cold solder joint at the resistor block;
CP1-CP4 in the PLL unit."
        I had the same problem, and this cured it..  BTW  I found that the best way to resolder the joints to CP1-CP4, was 
to scrape the paint off the trace a fraction out from the pins, solder to the trace, and let the solder run back to the 
pins. I created shorts between pins, when I tried to solder directly to them.. I also soldered some of the plated through 
holes in the vicinity of CP1-CP4, and it was cured..  Use a good iron...NOT TOO HOT!
      Good luck OM
                      John EI7BA

Counter measure against cold solder joint at the resistor block; CP1-CP4 in the PLL unit.  
Sub-band reception is deteriorate or receiving audio is intermittent distortion.
Transmission monitoring audio is distorted.
If you find the malfunction at stated above, take the following procedure. 
Cold solder joint of resistor block; CP1-CP4 in the PLL unit (X50-3170-00). In the manufacturing process, the temperature 
in the reflow soldering furnace was lower than specified and the connection was insufficient. 
Temporary: Add more solder to the resistor block; CP1-CP4 (at all pins) in measure the PLL unit (X50-3170-00).
Permanent: review the whole temperature control system of the reflow furnace to manufacture the Printed Circuit Board at more adequate temperature. 
PC Board (Component side view).



From: "Jeff King" <

To: <

Sent: Wednesday, February 23, 2005 11:24 PM

Subject: CQ KA5IPF Questions about how to diagnose TS950sdx  faults



Hi Cliff,

"Counter measure against cold solder joint at the resistor block; CP1-CP4 in the PLL unit..htm:"

This came from www.mods.DK. I have no idea if this is a known or  reliable fix for the 950 because the origin is not shown. It sounds like

my problem, excepting the failure of comp meter. Have you seen this before Clif, or do you know anything about this repair?

I look forward to receiving your advice.

Yours sincerely

Jeff King ZL4AI


From: Clif Holland []

Sent: Friday, 25 February 2005 12:39 p.m.


Subject: Re: CQ KA5IPF Questions about how to diagnose TS950sdx x faults


That is a very common repair on the 950's. The SDX was supposed to have been fixed though. I would try it and see what happens, other than that [and previous advice on making sure there is good RF ground] I don't have any ideas.


Clif Holland, KA5IPF



ZL4AI  emailed symptoms to

 John Tait []:

John advised:

 Distorted TX audio could be to do with the CP1-CP4 thingy.. On mine, at the start, it ONLY happened with the ATU in circuit. In other words, when there was RF around the CP1-CP4 chips. With an Amp in circuit, the amount of stray RF around the shack is increased.

My processor meter was not affected and continued to function.



ZL4AI Question to EI7BA: 
Has this “Countermeasure against cold solder joint at the resistor block; CP1-CP4 in the PLL unit" repair worked over the long term, 
and is your 950sdx still working well?

I sold it to my neighbour EI8HT.... It has work flawlessly..I'm trying to buy it back..{:o)




 ZL4AI  emailed AA5B the above symptoms as well

AA5B replied:

 Jeff -

The problems you describe in your eMail sound just like mine.

The repair guy who fixed mine said that it was a classic/common problem, and that re-soldering a few parts in the PLL fixed it up very nicely.


His name is Randy Starace, eMail

Web site:

Good luck!

    -Bruce AA5B




From: Jeff King []

Sent: Friday, 25 February 2005 3:04 p.m.

To: ''

Subject: Advice on how to fix TS950sdx faults.



I have a TS-950SDX with faults described below. The internet has led me to believe that you may know how to fix the problem 3, as you have fixed problem 3 in the past. Please see the referral about your advice below.




0. Comp meter has stopped functioning.


1. Leave TS-950SDX on receive only for 7 hours no receive problems at all.


3. After 20 to 40 minutes (simultaneous listening and transmission)receiver (only tested on USB) goes distorted (raspy) and stays distorted [and unintelligible].  Like you are tuned way off frequency. The transmission audio also become distorted. If you turn radio off and on, the distortion clears for a couple of minutes, but then comes  back.  This distortion seems to start at the top of the band and progressively covers the whole band. It can be distorted at the top of the band but clear at the bottom.


2. If I use the SB221 amp then this seems to set off the distortion sooner. I have substantially rebuilt and improved the new ground which seems to have decreased the onset of distortion.



attached is: "Countermeasure against cold solder joint at the resistor block;

CP1-CP4 in the PLL unit..htm:"

This came from www.mods.DK. I have no idea if this is a known or reliable fix for the 950 because the origin is not shown. It sounds like my problem, excepting the failure of comp meter.



I look forward to receiving your advice.


Yours sincerely

Jeff King ZL4AI




From: Randy Starace []

Sent: Friday, 25 February 2005 3:12 p.m.


Subject: Re: Advice on how to fix TS950sdx faults.


HI Jeff,  yes that is the fix,   do all the resistor packs on the DDS board and you will have it fixed

No need to solder the ICs 3 or 4.


Randy Starace





The Repair:

ZL4AI was nervous about soldering Surface mount technology and CMOS sensitive devices:

Solution was as follows:

-         Obtain Hakko 936 ESD safe soldering station, with Hakko 907 ESD safe iron,

-         Obtain Hakko tip 900-T-0.5C.  As you can see this is very small and thin, and helps to prevent too much solder, and heat to be transmitted to the CP pins. In fact when soldering against the larger foil areas of the board I had to turn the temperature of the station well up to get the solder to melt. At least this way you are very safe and sure you will not damage the TS-950sdx boards


-         Obtain a working desk with anti static mat [with a high resistive connection to earth to prevent any current flow through your work surface], and a floor mat earthed and an earthed wrist strap so you discharge your self before you touch any components.

-         Obtain rework solder flux: I used Electrolube SMFL Rework solder flux. This was really the major factor that made soldering the CP pins so easy.

-         Soldering: For each pin first I carefully scrapped off the paint coating with sharp craft knife. I also scrapped each pin of the CPP unit with the knife to remove the oxide. Then I sprayed on the SMFL, put a slight amount of solder on the small iron tip. Applied the tip, and because of the flux it immediately flowed. Down the pc board trace and the pin on the CP. The small amount of solder on the small trip meant I had no occurrences of solder bridges. And that SMFL just enabled solder to flow immediately.

-         After the first couple I found it was faster and best to scratch the up say 10 pins and traces at a time, spray the SMFL once, and progressively solder all 10.

-         On each CP unit not all pins are connected, so only some require soldering. Those to be soldered are:

-         CP1 1, 2, 3, 4, 5, 6, 7, 10,16.

-         CP2 1, 4, 5, 6, 7, 8, 9, 14.

-         CP2 1, 2, 3, 4, 5, 6, 7, 10,16.

-         CP4 1, 4, 5, 6, 7, 8, 9, 14.

-         There is no way I could re-solder CP4 connector 14 to CP3 connector 10 because the traces are underneath the CPs. So this connector was not re-soldered.

In the circuit diagram from the Service Manual below you can see how to identify these pins.





When I removed the PLL board found 14 holes where solder had not gone right through the board. Marked with arrows. If you blow up this picture you can actually see the empty holes. I soldered all up these up.



From: Traian Belinas []
Sent: Tuesday, 7 March 2006 8:47 p.m.
Subject: Re: TS_950SDX. request for expert advice

Jeff,  The holes are plated (conductive).
When wave soldered, some of the plated holes will be unintentionally filled with solder.
The solder have not to pass through holes!
So, the empty holes are ok, no need for soldering them!!!
Just check for continuity from one side to the other of the PCB holes and will see it.

I believe Traian’s advice, but as I had the board out it was not a difficult to re-solder the holes to remove all doubt.


It is worth mentioning that before soldering I checked each circuit with an ohm meter. They were all connecting.




The Outcome;

Turned on the 950sdx and the problem the raspy audio was gone. Have run the radio for many hours now for two weeks and it seems to be permanently fixed. Wow thank you to all who gave me email advice. [This has saved me the risk and huge expense of sending the 950sdx 2,000 kms to Kenwood Australia.]


Raspy Audio sequel took a second repair:

Worked well for 5 weeks. THEN …… Blasted raspy audio again!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Can you imagine my frustration when the fault returned?

The fault was not as severe as before, and it came and went, while using the 950.

If I turned off the radio for 2 min raspy audio cleared.

After a while I thought I wonder if it is that CP4 connector 14 to CP3 connector 10?


So with PLL board out again, I put an ohm meter on this connection. NO CIRCUIT! FROM CONNECTOR 14 TO CONNECTOR 10

Couldn’t believe it. The resistance actually measured at 13.59 Mega Ohms.

At last I was able to measure the lack of connection. [So the advice is try measuring for the broken circuit(, but the connection may measure connected as this circuit had previously).]

I did melt the solder on these joints and it was circuit gain.


Not being entirely convinced these were good solder joints, I soldered an insulated jumper wire in parallel between them, to be absolutely sure.


As these connector 10 and 14 are the worst to get at, I would repair this joint first.



The Return of Raspy Audio: Third Repair

Symptoms: Transceiver running for 1.5 hours,


Testing with signal general to deliver a S9 signal to antenna input, when operating with a region where audio was functioning

Tuning up band, heard in speaker audio as follows:



14330 and below OK no unusual sounds pure sine wave sound ti\one

14337: very slight cackle


14345: small cackles


14360: hear sine wave tone but mostly cackle

14370 mostly cackle

14380: just cackle noise


14395: cackle


14418 s9 signal gone

14443: s9 signal gone


14490 ok sine wave

14505 ok sine wave

14697 ok sine wave


Established that running radio for 7.5 hours with case open for malfunction does not occur, so probably heat related.


Wondered if problem could still be a faulty CP1 to CP4 connection.

Drew out a better working diagram, below (this time it is as you look at the board)

and set out with an ohm meter……………………. To re-measure connections again!

CP3-16 to R136 measured as open circuit.      >>>>>>>> Same old problem.

Soldered a jumper wire from CP3-16 to nearby through board connector to R136.

Ran for 9 hours and audio now appears fixed again. Hope it does not appear again! These CP connectors are difficult to obtain a fully soldered joint.













 VCO 2 Problem

From: "Paul McInnish - K4BET" <
To: "Kenwood Reflector" <
Sent: Wednesday, April 03, 2002 6:17 AM
Subject: [Kenwood] TS-950SDX Problem 

After being turned on for 30-45 minutes, the audio on my -950SDX starts to distort,

gradually deteriorates to complete un-intelligibility and finally
will get a CW beeping (I believe the CW that is sent is the letters "AL"),
display digits goes almost blank (except a row of dots) and nothing works
(will not xmit, receive, display on the SM-230 is a straight line etc.,

Turn it off for 15-20 minutes, works fine and the deterioration starts
again.  Sounds like a heat problem.... but would be interested to know if
anyone else has had the same problem and the resolution?!?!

Anyone got any thoughts?


John Tait suggested:

Now the possibility of a problem with VCO 2 rears it's head... This is a well known problem on the TS850s, where the VCO goes out of adjustment, or one of the DDS chips goes flakey. I have NOT seen this on a 950 (yet), but I can do the adjustment on an 850 blindfolded, as it's such a common problem.

The following from Clif tells how to check the 950 adjustment..

John Tait



"On the AF unit (bottom of radio, left front, with knobs to you) locate the
smaller enclosed VCO. Beside it is TP2. Using a insulated adjusting tool
turn the small trimmer cap in the VCO several times to remove oxidation. The
set it to 5v measured at TP2 using a voltmeter. 

This is the enclosed area with only one hole in it. DO NOT TOUCH the one
with 4 holes. 

Clif Holland, KA5IPF
Authorized Kenwood and Icom Amateur Service











Subject: [Kenwood] TS 950SD



I have lost the frequency display on my 950.  Turning the dial will

cause the display to return for about one second then the cw coded

message "UL" is sent and the frequency display goes out again.  I

assume that the "UL" means the frequency synthesizer is "unlocked".

Any ideas where to start my search?

Resetting the microprocessor does not help.



Mike W7AJ



*Hi Mike..

Check out  Jeff King's site at

 Jeff has done a great job of collecting all sorts of useful info for

SDX users.

  Scroll down his page to "VCO2 Problems" This one seems the most likely

cause of your problem.

Vy 73

    John EI7BA*





-----Original Message-----
From: [] On Behalf Of
Sent: Saturday, 6 May 2006 3:59 a.m.
Subject: Re: [Kenwood] TS 950SD


I'm pleased to say that with the help I received regarding my 950 problem, the reference to the VCO 2 probelm was also  my problem.  The test point 2 next to the VCO2 was reading about 0.680 volts.  By turning the trimmer several times to remove any oxidation, the 950 came back to life.  I set the voltage to 5.0 vdc and all appears to be okay again.

This is the only problem in about sixteen years of ownership.  One exception to that however was three pot. connections in the auto tuner that had never been soldered at the factory.

Thanks for the help!

Mike W7AJ





Thanks!  That solved my problem.


Mike W7AJ



-----Original Message-----
From: John Tait []
Sent: Friday, 5 May 2006 8:35 p.m.
To: Jeff King
Subject: K7AJ


*Hello Jeff..

               See below .. Another scalp for your Totem Pole.. {:o)

Your site is saving me a lot of effort. I don't have to write long

emails anymore..

I just refer them to your site..

     Vy 73

       John EI7BadApples














The following is very clever way to use another Kenwood radio eliminate one section or other of the radio as functioning correctly. 


From: Traian Belinas []
Sent: Tuesday, 7 March 2006 8:47 p.m.
Subject: Re: TS_950SDX. request for expert advice


You may use also an "intelligent" way of detecting the problem stage, an idea that just appeared to me.
It may be the PLL, the mic preamp, the balanced modulator, tx IF stage, etc.
You have the TS940 at hand, is it?
The both 950 and 940 are using the same IFs?! I think they do.
So, you may couple and listen the 455kHz Tx IF signal from the 950 to the 940 455 kHz Rx IF!
The same for the 8,83MHz IF.
A problem will be the signal levels, as the Tx chain levels from the 950 shall be too high for the Rx chain of the 940, so a ressistor shall be used for atenuating it.
Or may just coupling them as the 950 Tx IF to induce Rx signal on the 940 (capacitive coupling, may not need direct conection).
Another problem shall be avoiding radiating HF RF, so always use a dummy load for the 950 and disconnect the 940 IF from its RF unit.
I don't remember exactly, but small coaxial cables/connectors are used for the IF signal connections, so it may be easier than it looks...





Battery Replacement

Berry W6EZ
Sun, 28 Dec 2003 08:05:16 -0800

I just bought a TS-950SDX and I wondered what shape the memory back up battery
might be in.
After reading all the horror stories about battery leakage ruining the traces on the boards they are mounted 
on in the 850s, I thought it would be a good idea to check the 950 for the possibility of the same problem. 
As it turned out, my fears were well founded. Once I removed the top and bottom covers of the radio, 
tilted the front panel forward I immediately noticed the tell tale signs of battery leakage, namely a 
discoloration of the plating on the battery case.
Fortunately, I bought two of the batteries from Kenwood (it never hurts to have a backup) 
so I had the parts and did the job while I had everything apart. The battery in my TS950SDX was the 
same as in my 850.
I have uploaded a set of photos to
in the photos area and each photo has a caption that will help explain
what you are looking at in each picture.
This is not a hard job to do, from start to finish it was less than an hour, but I do have 
a desoldering tool and that helps a lot.
the part number from Pacific Coast Parts is: KW09-0514-05 it costs about $9.00

Another possible source of replacement memory batteries for the TS-
950SDX is Mouser Electronics. I just received a battery I ordered
from Mouser (along with a bunch of other parts), and it is identical
to the replacement battery I ordered a week ago from East Coast
Transistor Parts, Inc. The only difference was the price. East
Coast charged $9.71 for the battery. The price at Mouser was $2.30.
Both batteries are Sanyo CR2430 lithium batteries and the both have
identical PC board leads spot welded to them. For those who may be
interested, the Mouser part number is 639-CR2430-FT1. (Note: Mfg
P.N. CR2430-FT1). Mouser's web site is
Phone: 1-800-346-6873.

Frank (KKØK)













Jumping Frequencies all  by Itself: Solution still Required

-----Original Message-----

From: Michael Ditmore []

Sent: Sunday, 23 July 2006 7:42 a.m.

To: International Radio


Subject: Re: 950SDX


Dear Jeff and George


This is the most (and fastest) feedback I have ever had on a 950!



I am about to do the battery replacement + MARS freq mods and will also put on a new front panel at the same time ($77 from Kenwood parts)... if I'm feeling gutsy after that I'm planning to tackle some of the crazy guy's mods (WZ5Q) which look interesting – especially the audio line input.


Right now I am running a Symetrix 528e right into the normal mic input and getting great reports (think how much better it could be :-)


As I said, I am plagued on 75 (only) by these intermittent jumps in IMD and can only imagine leaky diodes (temp driven) as the cause.


 From time to time the rig will jump down to a freq of 1.71xxx on its own and I suspect this is the low battery or some faulty inter-board connection.


Again, best of thanks and please put me on your 950 distribution.







On Jul 23, 2006, at 12:18 AM, Jeff King wrote:



If you prepare am email with a full description of your 950s IMD symptoms, I am more than happy to post it on the 950 page. Someone maybe more  than happy to provide a solution.

Freezing suspect capacitors sounds an good idea.


Yours sincerely

Jeff King






-----Original Message-----
From: Michael Ditmore []
Sent: Tuesday, 17 October 2006 5:01 p.m.
Subject: Re: 950SDX




This is an update to the message below -


I successfully performed the battery replacement and MARS mods this  weekend and the 950SDX seemed to be back to its old self... no more  IMD problems.


However 24 hours later one original problem has reappeared.


I will be receiving on 75 and without warning the VFO (in this case 

A) will beep once and switch to 1.8 MHz


Memory functions are fine and I can return immediately to the  original frequency, sometimes for seconds, sometimes for hours, until  it happens again.


New battery, no other symptoms.


Anyone else seen this?














----- Original Message -----

From: "Bob Arenella" <

To: <

Sent: Sunday, September 30, 2007 10:03 PM

Subject: [Kenwood] Sick TS-950S



Hello all,

                  New to the list. I recently picked up a TS-950S that has a problem. I found the 7.5 amp fuse in the power supply was blown. Replace it, powered up & the display came on for a fraction of a second & fuse blew again. I don't know the history of this rig, as the seller was not a ham. He knew it had a problem & sold it for a price so low I couldn't pass it up.







Most likely, shorted finals.


Clif Holland KA5IPF









Preventing Final FETs failure      


Contact author.        Contact author:

Tony, I0JX


My suggestion is to replace the two 22-ohm 0.5-W resistors marked R15 and R16 with carbon-type resistors of same value but higher power (e.g. 1 W).


Those resistors are located in the "Final Unit", not too far away from the final Field Effect Transistors (FETs). Replacing them is fairly easy. The rationale for the proposed modification follows.


I have my TS-950SDX since about 13 years. In year 2004, the final FET marked Q4 2/2 unexpectedly failed, with no apparent reason. A circuit check showed no problem whatsoever, therefore I attributed the failure to an occasional fault, and I then just replaced the faulty FET with a new one. But in year 2005 it failed again. Then, before replacing the FET another time, I performed a very accurate circuit check.


With the aid of a magnifying lens, I realized that resistor R16 had got a bit deformed at its center, taking a "barrel" shape. After carefully inspecting and testing that resistor, it was evident that it had overheated and that it was subjected to an intermittent contact.

At times when that R16 opens up, the RF drive voltage on FET Q4 2/2 gate grows up a lot, causing its failure. Evidently that resistor is undersized, as it does not withstand the applied RF drive power.




ZL4AI found R15 and R16 measured 22.4 ohms and 22.7 ohms. (Maybe they are deteriorating? Unknown if theses are 5% tolerance resistors. If they are 5% tolerance upper value is 23.1 ohms )


Replaced with from RS Components

477-1510 RES METAL OXFILM 1W 22 OHM 5% Matsushita Electric Industrial. These measured 21.9 to 22.0 ohms.


After replacement I thought it was important to adjust the final unit voltage and current for new components

Service manual page 199 item 9 defines how to set up

Final Vcc

Drive Icc

Final Id


Note that Drive Icc and Final Idd are set in USB mode.

NOTE THIS WELL BECAUSE I TRIED TO SET Final Idd in CW mode, and it overshot to give reading on 150 mV approx,

There was flash, and Q4 ½ and Q18 were destroyed.

Not a happy repairer who had been undertaking preventative maintenance.


In hind sight I would have been better to wait until finals failed before replacing them.



Caution just progressively turn these potentiometers up to required voltage setting. Do not turn potentiometers higher than the specified limits. The safest way is to not transmit. Turn the put up a milli fraction of a turn. Transmit and quickly stop transmitting if you have turned too far. Slowly does it there is no reason to rush like I did and make a $250 mistake.





Using multi meter to check if finals are ok?

Disconnect the or take the following components off the final board by unsoldering:


Off the board

Q18, Q19



Unsolder 1 lead

C48, C49 C50, C51

C42, C43, C44, C45, C46, C47

R15, R16, R17, R18


This lead the gates of the MRF150s open.


Use to multi-meters to test.


Connect 1 between reading resistance between the drains and ground. Ie. Across the drain to source. 

For the good transistor This read about 5.6K once the meter stabilised.


Use the other meter set in diode test mode to apply voltage between the gate and source. Use no more than 2.6 volts. Check this voltage with the other meter before you apply it.

If the transistor is working it will turn on, and the drain to source resistance will drop to 13 ohms.


Then reverse the 2.6 volts on the gate to source and this will turn the MRF150 off and it will read 5.6K again.



In the MRF150 I had destroyed:

-          gate to source measured resistance about 23.3 Mega ohms.

-          On good MRF150s gate to source resistance or gate to drain resistance showed no connection whatsoever.


On good MRF150s drain to source varied a lot, between, 5.5 kilo ohms, 16.25 kilo ohms, 0.12 mega ohms,  0.62 Mega ohms



Data Sheets for MRF150s are here:


The original is Motorola


The semi conductor division of Motorola was sold to M/ACom.


So in effect M/Acom are identical, and seem to be cheaper to buy.








The MRF150s are Mosfets and are very easily damaged by static electricity.  Especially the gate connector is very sensitive. So there are special steps to soldering them in. beware you could destroy them by touching them.


1.      Work with wrist strap grounding you to your radio ground wire,

2.      Ground your soldering iron tip, bay wrapping wire round the barrel and attaching that to your radio ground wire,

3.      work on a grounded surface. I found the idea was the 950sdx heat sink where the finals came out of. I just attached that to the radio ground wire.


That way all 3 items were at zero volts, and there was lots of metal in the radio body for my hand to touch to be sure they remained free of static charges.


Now take the new MRF150 transistors and tin the gold connectors. Easiest way is to use one screw and attach them to the grounded heat sink as soon as they come out of the antistatic wrapping.


After that get a very thin copper wire and solder it in a ring (on the top side) around the 4 connector tabs. Now you have the transistor in a safer handling state


Bolt the finals board to the heat sink. Screw the new MRF150s in place. Then progressively solder on each gold tab to the board. 


After that slowly unsolder the ring wire and remove it.


Take careful note of where the two insulating Mica Washers / spacers insulate Q1 and Q8 from the heatsink. Neither of these transistors is grounded, and the  Q1 also has plastic washers insulating the attachment screw from the body. This point is not well explained or illustrated, in the service manual










Not recommended practice / This is the wrong way to set up finals

After I blew up Q4 1/2  and Q18:


I found that VR4 on my radio made no difference where it was turned.  ???

Turning VR5 was effective set TP2 voltage up to 90 to 110 millivolts.


So I was puzzled as to how to set VR4 correctly so as to not put excessive current into the transistors.

The schematic on page 227 shows transmit voltage at the emitter of Q18 to be 2.3 volts.

VR4 adjusts the base of Q18.

On transmit I used a digital volt meter and turned VR4 to set the emitter of Q18 to be 2.3 volts.

Then I turned VR5 to set up TP2 to read 104 millivolts after 1 min of transmit. TP2 reads about 90 millivolts after 10 seconds of transmit and slowly climbs to 104 millivolts over the next 50 seconds.

VR5 adjusts the base on Q5.

Then I measured the emitter of Q5 at 3.1 volts. The schematic on page 227 shows transmit voltage at the emitter of Q19 to be 2.6 volts. [So this is reading 0.5 volts higher than spec]


There is specified differential of 0.3 volts 2.3v compared with 2.6v between the emitters of Q18 and Q19.

Possibly it might be better to achieved a more balanced condition than 2.3 and 3.1.

This could be done by adjusting VR4 to give slightly higher voltage say 2.5 volts at the emitter of Q18. Then reset VR5 to give 90 to 110 millivolts at TP2.



When I used the radio setup like this I found I got:

180 watts output  on 40 meters,

120 watts on 20 meters

And 80 watts on 10 meters


In fact I believe I was getting this output out of just 1 transistor.

The MRF150 outputs 300 watts so this is possible.


VR5 should only be set up to give 50mV at TP2.














Hallo Jeff de Gabriele I4JXE,

 I'm trying to fix a fault in my Kenwood TS-950SD s.n. 30600007, and a true Good source was yor internet site. TNX

 The audio signal out of the speaker became barely  perceptible even with the control full turned. The same  coming by the sub-receiver. With the knob from middle to  back no audio out a all. As with headphones into EXT SPK  jack (the same happens at the speaker leads, with speaker  removed) I hear a correct audio signal, I guessed that the  AF PA (ic7 in the control borad) was burned out, so I  replaced it (a common operational amplifier TDA 2002), but

 no luck, and still no audio. I have a complete set of  repairing instruments, any suggestion to try to fix it by  myself? (no help from the Kenwood service bullettins)

 TIA es '73





 Subject: Re: Requesting help on TS-950SD

 Date: Tue, 12 Jun 2007 15:59:33 +1200


 Quick Suggestion:

 Get Service manual

 Find signal level diagrams for transmit signal.

 In middle of manual. on one page only


 THis requires injecting signal generator signal in antenna  and measuring tracing the signal through the entire path.

 Use this to identify where the signal decreases. then you should be bale to work though and identify which components

 have failed.


 Good luck

 sounds like you will achieve repair.

 Be interested to hear how you get on

 Yours sincerely

 Jeff King



From: gabriele i4jxe []

Sent: Wednesday, 13 June 2007 3:17 p.m.


Subject: RE: Requesting help on TS-950SD


Rig repaired !

As I told you there was only an almost complete lack of audio output in my TS950SD, that anyway continued to work fine.

I usually work digital modes, with computer interface delivering the fixed audio out from the connector on the rear, so it wasn’t really

a big problem to me, but decided to bring back the rig to complete good health status.

I localized the fault in the control unit board (X53-3230-00), where the audio output from pin 4 of the amplifier IC7 (that is a TDA 2002)

Couldn’t go to the speaker across the polarized capacitor C7, a 220 microF./10v., that was open.

I changed it with a 220 microF./25v. one that look me more correct for the duty, and the job was done.

Doing the job, I suggest to change even the two other capacitors near C7, C3 (1000 mF./16v) and C6 (470 mF./6,3v),

raising the working voltage to 25v.-

The AF amplifier microPC2002v IC7, that is a TDA 2002, should be changed with a TDA 2003, delivering a little more output power.

Again congrats for the good work for the Kenwood 940/950 family owners I will be glad to contribute to in the future.

Best regards

'73 de Gabriele, I4JXE








The terrible no volume 50 hertz audio hum. That drove me nuts

Fixed in Jan 2008

When ZL4AI turned the volume right down, there was this really irritating low level hum sounded like a power supply 50 hertz.

Tuned volume up and the hum disappeared into audio noise.

As I listen with headphones this really irritated me.

[How did I notice this? I have a 940 and 950sdx in A / B positions. Often I use the 940. the 940 has a very good receiver and really only the DSP quietness of the 950SDX appears to be better. At no volume the 940 was no noise at all…. But the 950SDX had this infuriating hum!]

I always wondered if this hum was not present, I would hear signals at low volume more clearly. I certainly could turn the 940 down into almost no volume with a very noisy band and often copy really improved. The almost no volume improvement was not possible with the 950SDX.

[If you have experienced turning volume right down and improving your copy, then you will understand what I mean].

For sure there was distinct possibility that the radio would be distinctly improved at DX low signal level copy.

[After fixing this, I can tell you the radio is considerably improved as a receiver. I now can 940 low audio level calrrity. The improvemet was worth very minute of the effort to find the problem]

For sure a $4,000 radio should not have this HUM.

But… how to find it / fix it ???????????????





What follows is probably really useful as a methodology.

I worked back wards up audio chain to eliminate all possible sources of sound, block unit by block unit.

Disconnected main audio feeds into each block to find the feed the sound came form.


A: Look at functional block diagram page 15 of Manual which shows the general sequence of audio signals.

B: Then look at Main schematic diagram p296, to see each of the connector numbers.

You will have work your way backwards and forward between A and B to figure out where each (audio or RF)  signal comes from / to.

Then from the Main schematic diagram follow through these descriptions on the individual circuit board drawings for the Control Board, AF Board Switch board etc.


Note that SINGLE each wire is disconnected by taking off the connector and carefully removing the SINGLE wire OUT from the connector, and then reconnecting the other wires at the connector. This enables elimination of the problem SINGLE wire by SINGLE wire, signal by signal, and ground shield wire by ground shield wire. This single signal by signal elimination was the key to finding the fault.

BE CAREFUL NO TO REMOVE control wires that could result in damage to a board component. Only remove a wire when you have verified it is an incoming RF or audio signal.


The following sequence is Working progressively up stream.


Control Unit

Connector 9 disconnected: hum still there. Sub-receiver is not source

Connector 8 disconnected: hum GONE. Main receiver is source, and this comes form the AF board.


AF Board:

Tried disconnecting main inputs to this board.

Sequence below is important


Disconnect W1: main receiver input from signal unit: Hum still there: This is not source


Disconnect Connector 14-2 output from AF volume control: hums increases in level

Disconnect Connector 13-2 input from AF volume control: hums is gone

Reconnect Connector 14-2 and hum returns



Disconnect both 14-2 and 13-2 and hum disappears

Connected both 14-2 and 13-2 and hum is quite low level

Disconnect either 14-2 and 13-2 and hum is louder


Connector 13-4 produces most hum and level increases as monitor circuit volume is turned up


Wondered if fault was fixed by Service Bulletin ASB 1050?

Installed 0.01 uF disc ceramic capacitor  on switch X41-3520-B/10 as described in Service Bulletin ASB 1050.

All hum related to disconnecting AF Connector 14-3 disappeared completely….. Partial Success!


Following ASB 1050, and

Removed Control Board. And

….. all of C33, C34, C39 had already been installed as tantalium capacitors.

Observe that this radio already had ASB 1050 partially undertaken.

Note that it is worth verifying the modifications have been made because in this case only part of the modification was installed.




Now try Eliminating further other input signals to the AF Board


Disconnected connector 3-6 which is to IF board 15-SAF: hum is still present.


Found at Connector 12 wire 5 which is ground shield for wire 4- to SWA J/10-108-MONVRI was incorrectly connected  to pin 3. and hence was not grounded at all. Shifted this ground wire back to pip 5.

Note my 950sdx is very original and mint condition. I am the third owner. As best I can tell I am the only person who has ever worked on this radio.

First owner was a short wave listener. Second won a collector who did not sue his radios much.

It is likely this ground wire in wrong place was factory error.

Changing the ground made no difference and the hum is still present.


Disconnected Connector 12-4: Hum still there, so  hum no induced by monitor circuit.


Removed DRU2 units and hum still present, so not introduced by DRU2 circuits.


So traced from Connector 13-4 which is to SW A –E10 Connector 18-7 MONVR2:

Disconnected SW A –E10 Connector 18-7 and HUM IS GONE!

So source of  Hum is SWA E/10


SWA E/10

 Disconnected Connector 20-6 MONVR1: hum is still present.


Concluded hum must be coming ground leads to switch or in the switch itself.

As monitor volume is turned down MONVR2 has 10K ohms between its signal and earth, and the hums disappears.

This means the hum must becoming up the MONVR2 ground wire Connector 18-6 or Connector 20-5

Disconnected Connector 20-5 and THE HUM IS GONE!

Other end of Connector 20-5 is SW A  J/10 Connector 109-2-GND


SW A J/10

Disconnected Connector 109-2-GND and hum is also gone.

FOUND THE HUM. It is in this ground wire Connector SW A  E/10 Connector 20-5     to     SW A  J/10 Connector 109-2-GND


So how to leave this ground wire connected with no hum?

ARRL hand book 2004 recommends 0.01 uF disc ceramic capacitor to remove low frequency hums.

Permanent solution.

Permanently removed 109-2-GND  form SW A  J/10 Connector 109.

Soldered a 0.01uF disc ceramic capacitor to wire and another pi connector and pushed this into Connector 109-2-GND. The otther capacitor wire went to the removed  109-2-GND  metal female socket. This was covered with insulation tape.


This is one modification you will never regret. 

 Also note. Only tools required were an ohm meter, a service manual, a soldering iron and small pliers.








1.8 Khz filter PROBLEM ???

-----Original Message-----
Subject: [Kenwood] 950SDX PROBLEM ???
Hi All,
         I may have a problem with my 950SDX---late model Mfd. in 1998. When I'm listening to 
upper sideband, and select the 1.8 khz. filter, in order to have the audio sound good, I must take 
the "high cut" slope tune knob and turn it 2 or 3 clicks counter-clockwise. If I do not, it sounds tinny. 
It does not do this when listening on lower ideband, only on upper.
Those of you with 950SDX's and the 1.8 filter installed, please try this--let me know if yours does 
this also. If you do not have a 950SDX and might know what the problem is, please let me know too. 
940 & 850 users---please try it and let me know your results.
                     RON GOLDSTEIN--KA2IIA
                      PUTNAM VALLEY, N.Y.


Dave Jaksa
Mon, 2 Sep 2002 14:46:25 -0500

That's the way mine has always worked and I have seen the same thing on two
other TS-950's that I have used.  I think it is a simple matter of having
the narrow 8.83 MHz SSB filter in there.
I also notice some of the same thing on LSB but to a much lesser extent.
Since I'm usually interested in a tighter bandpass when I use the 1.8 KHz
filter, I usually run the High Cut between the 3 and 4 o'clock position when
I switch it in.
Dave, W0VX



Mon, 2 Sep 2002 16:13:55 -0400



 The 950sdx carrier point ( receive only on the 950) is align for the 2.7khz filters. Anytime you go to other filter widths you have to recalibrate the

slope tuning to match the filter... This is normal with all radio , whether it has slope tuning or IF shift.. Unless the filters are DSP based like the 756 Pro or TS-870


73 john








RM-1 Controller required for full control

Bud Hippisley, K2KIR

Sun, 09 Mar 2003 23:38:06 -0500

There is no front-panel way to run CW or voice messages on the TS-950SDX.  There _is_ such ability on the TS-850 -- at least for CW; I can't vouch for voice.

Rus Healy's review of the TS-950SDX in QST a decade or so ago specifically noted that the 950SDX was the first instance he knew of where the remote control provided (message) functionality not available on the front panel of the HF transceiver.

And yes, although the manual is not real clear on this point, you always get the CW message capability with a stock 950SDX -- but you must add the DRU-2 option to get voice message capability.

There is nothing magical about an RM-1.  It's basically a few switches and a bunch of precision resistors.  The switches switch different resistor values onto the hot lead of the shielded audio cable going from the RM-1 back to the jack on the rear of the transceiver.  A simple A/D conversion circuit inside the 950SDX changes those different DC voltages into a variety of logical commands (one at a time, of course -- you can have only one DC voltage on the cable at a time).  You can build up an RM-1 out of your junkbox parts or after a quick visit to Radio Shack.

Bud, K2KIR








Service Menu Warning

-----Original Message-----

Sent: Friday, March 03, 2006 7:13 AM


Subject: Re: [Kenwood] kenwood TS-950SDX



james rich wrote:

Can someone tell me how to turn up the output  power of this radio, I'm not sure what VR to  turn,,,Thanks,,James //



My observation If you come into the service menu(3+9 and power switch on), the power is dropped to 100 watts, Even if to not touch an position 9 (100/150w), before an exit it is necessary to choose from the service menu In an position 9 - 150, and then to switch off or clr key


73! Ilya , RA4CTR



From: on behalf of Hsu, Aaron (NBC Universal) []

Sent: Saturday, 4 March 2006 8:19 a.m.

Word of warning...


If I remember correctly, Cliff from Avvid warned to never enter the "service" menu as some settings are reset to default just by entering the mode.  This implies that the radio would no longer be operating at "optimum" or possibly out of alignment.  He never posted any "service menu" power-on key combinations due to this and always informed people not to do it without just cause.


Ilya, this might explain why the radio dropped to 100 watts - it might be the "default" setting of the 950.  Hopefully, no other settings in your particular 950 were affected, but you can't tell unless you have test equipment to verify.


  - Aaron, NN6O






Part of DSP Circuit is missing

ZL4AI noticed on his radio there was no connector 9 into the Digital board? What????

I don’t really understand this because the circuit is there in the circuit diagrams. It looks important!




Not only is connector 9 missing in my radio, but also that on W6EZs radio above. In the photos of battery replacement above “labelled 4 connectors (1 ribbon and 3 pins) are removed to allow the board to tilt forward”, you can see there is no plug in connector 9 which is empty to the left and below the battery. It appears to me an important part of the circuit to the DSP is missing. As well on the IF Board I also found there was no plug in connector 25. Any advice or information about these missing plugs would be appreciated.












[Kenwood] TS950SDX filters

I have recently acquired a TS950SDX.  After adding the 250Hz cw filters in both the 8mHz and 455kHz 
positions, the radio will select all possible filter combinations in cw mode for the 455kHz position 
including 250 Hz.  It will NOT allow the selection of 250 Hz in the 8 mHz section.
How do you enable the ability to select 250 Hz in the 8 mHz filter system???
Tony Field (VE6YP)



Sun, 27 Jan 2002 20:11:32 +0000

you have to "rewrite the set menu". the complete instructions are on page 58 of the operating manual .
In brief:
Hold down the ENT button while powering the radio ON
use the MCH/VFO.CH knob to select  MENU #1
the use the UP/DOWN buttons to toggle the 8.83 MHz / 270 Hz filter ON

How I gave new ears to my TS-950sdx

by Alberto di Bene,  I2PHD

Once upon a time I wasn't especially interested in LF. To be honest, I didn't even know that we had 2.1 kHz of band allocated in the 137 kHz segment. So, when I bought a second hand Kenwood TS-850 I didn't pay consideration to the fact that on that band its receiver is an outperformer.
Then someone told me that Spectran could be used also for detecting and showing below-the-noise weak signals on that band, where terrible antenna inefficiencies are the norm, and rarely the EIRP reaches 1 W, even with 1 kW output power !

My interest for the 137 kHz band was borne, and only then I discovered that my TS-850 was considered one of the most sensitive receivers on this frequency. All went well, I built a preamplified loop and had excellent receptions of many European hams, and some commercial stations from all over the world, in the segment between 30 and 140 kHz.

Then, during June 2001 I was at a ham fair, where I saw on sale a second hand TS-950SDX, the big brother of the TS-850.
After a long and tiring negotiation with the merchant, we finally reached an agreement on the price I had to pay in addition to giving him my TS-850 in exchange for the 950. I went back home happy like a child with a new toy...

And it was then that I had a great disillusion... while the 950 performed flawlessly under any other aspect, its sensitivity on the LF band was nothing to be compared with that of the 850.  Plainly said, it was deaf as a doorknob on this frequency...
I went through different emotional stages, among which the consideration of killing the guy who sold it to me...:-)  but then, being the pseudo rational animal I deem myself, I calmed down and decided to investigate about the reasons of such deafness.

After perusing the schematic diagrams of both receivers, which do have remarkable similarities (logical enough), I spotted a difference that made me suspicious. Here is an excerpt of the RF Unit of the 950 :

If you pay attention, you will be able to spot near the center of the diagram the transformer L3, which is in the direct path between the antenna and the bank of 15 switchable bandpass filters. It is a broadband 1:4 impedance step-up toroidal transformer.  The 850 doesn't have such component, the input signal goes straight to the filters bank.       Hmmmm, very suspicious....

(BTW, you can also see in this diagram the infamous MW attenuator, R33, R34 and R35, that Kenwood insists on placing in all its receivers.
It does nothing useful. I have bypassed it with no adverse effects)

Well, the decision to replace that transformer was almost immediately taken. I searched the MiniCircuits catalog for a suitable unit, and did find what seemed the ideal one, the model T4-6T-KK81, with a 3 dB band from 20 kHz to 100 MHz. I had found it !
But Murphy wasn't sleeping at that time... I phoned to the Italian MiniCircuits distributor, and they told me that they didn't carry that item in stock, and, of course, they were willing to order it for me, how many tens I needed ?  Err, thanks I said, don't worry...
An email to the US MiniCircuits sales office did give similar results, they have a minimum amount for direct sales.

My only resort was then to ask for help on how to wind it myself on a few newsgroups I regularly read,
I even sent an email to the Customer Service of Kenwood Japan.  The answer I got was very japanese :

Dear Sir,

Thank you for your e-mail. Regarding your inquiry,
as you indicated, receiving sensitivity of TS-950SDX
in the low frequency band is inferior to the one of
TS-850. Regrettably, however, this receiving sensitivity
cannot be modified or improved by the change of parts,
etc.  We are obliged to ask you to use the model as
they are.

We are sorry that we cannot meet your requirement.
(Tokyo, Japan)
  Customer Service Section
    Kenwood Corporation

Not that I expected much more than this, but I had hoped at least that they confirmed (or denied) my suspects about L3....
But the real help came from two other directions.
Frank Gentges, K0BRA, had performed a similar operation on the Ten-Tec RX320 receiver, and he kindly offered me to wind a suitable toroidal transformer, based on that experience. Can you imagine me saying : No, thanks  ?? Neither can I, so I gladly accepted, and waited anxiously for an envelope from the States.
A few days after, David Bowman G0MRF, well known in the LF field for his projects of power amplifiers for that band, wrote me that the UK distributor of MiniCircuits had that part in stock, and, as he was about to order some other components from them he needed, it would have been easy for him to add my transformer to his order.  At this point it struck me the thought that perhaps Murphy were in a serious illness status that day, and that I had to take advantage from his temporary inability to render all my efforts vain.

I thanked David and accepted his offer. At this point I was checking the post office daily, waiting for two envelopes !
After about ten days (the Italian Mail Service is hardly notorious for the quality of its service...), the fate played one of its magics : the two envelopes arrived simultaneously !

Time to fire up the soldering iron, and to perform the transplant, with the heart beating at high rate : after all, I couldn't be absolutely sure that L3 was the culprit...

First operation, open the 950, find the RF Unit and that component :


The RF Unit has been isolated and disconnected from the rest of the transceiver. Now the delicate task of removing the original L3 without destroying it (after all, there was the possibility I had to put it back again...), nor damaging the PCB. 




Here it is the candidate culprit ! The quality of this and the other photos is not very high, but this is all what my camera is capable of.
The transformer has only 10 trifilar turns, and the core is rather small. No wonder at LF it isn't performing in a stellar way...

Ok, the first of the two replacement transformers has been soldered in place, the board resettled and all the connections restored.
A trembling finger presses the Power switch, and... nothing ! The radio is muted, only the faint hiss of the AF circuitry can be heard from the speaker... evidently Murphy has recovered from his illness...

Time to check everything carefully. There are 21 screws to unscrew to freely reach the RF Unit. At the 20th one, I saw what I did wrong when I had hastily reassembled the thing : a small coax cable arriving on the board wasn't properly reconnected.  Pheeew !
This time I switched on the radio before closing the covers. I know, I should have done this the first time, but I didn't.
I plead guilty, Your Honor.

But, SUCCESS ! This time the 950 was alive and sensitive as a young girl in springtime ! I checked both in the 10-meter band and at LF, and in both bands the radio performed well. On the 28 MHz I compared it using an A/B switch with another transceiver I have, and on LF I was able again to listen to the 77.5 kHz time signal from DCF77 and to hear the RTTY-like signal around 43 kHz. From a purely subjective point of view, the increase in sensitivity on the LF band can be deemed not less than at least 10 dB.

At this time I had the transceiver still open, so it was a matter of a couple of minutes to solder in the other replacement transformer I had received. No difference with the first. Both the MiniCircuits' and Frank's transformer worked equally well. This to testify the quality of the work done by Frank. Not that he needs this testimony, he is well renowned in the LF circles, but I owe him this.

This is picture of his transformer :



Frank did enclose with the transformer a comprehensive set of measurements done presumably with a Network Analyzer from 5Khz to 30 MHz.  Really a professional job !

For a DOC with the measurements done by Frank, please follow this link.

And this is the photo of the RF Unit with his transformer installed :


Ok, we are now at the end of this history of a change.  All is well what ends well, and this story did end very well.

The moral is twofold :

1) Don't think that the various Kenwood, Icom, Yaesu, etc. are infallible. Moreover, they have often cost justifications.
I have seen that the original L3 is used in many other parts of the radio. Using at the input stage a different model would have meant to have another item to add to the Bill Of Materials, with the added costs.

2) The Ham Spirit is still alive. Both Frank and David didn't have any other reason to help me but the Ham Spirit. And as long as it is alive, we can look with confidence at the future of Ham Radio.

Thanks Frank, Thanks David



TS-950SD general coverage transmit mod (1.8-30MHz Continuous TX)

TS-950 function Believed to work in the 950sdx

Remove the top and bottom covers (18 screws).

  1. Remove the top screw from each side of the front panel assembly.
  2. Loosen the bottom screw on each side of the front panel assembly.
  3. Carefully tilt the front panel forward to expose the Digital Board.
  4. Cut the lead of Diode "D-17" on the Digital Board.
  5. Reassemble the transceiver by reversing steps 1-5.
  6. Reset the CPU by pressing and holding the "A=B" button while
    powering up the transceiver via the "POWER" button.




Power On Funktions

TS-950 functions Believed to work in the 950sdx

Please notice that all functions only work if you switch off radio first.
Please push the named buttons to start function when switching on the radio:

SUB : SUB receiver capable of scanning to SUB-scan push and hold the SUB-key and press than the scan key

ENT : Set up ch. 90-99 as amateur band vfos 160-10 m band possible. each memory vfo will accept direct frequency entry.(like ICOM band stack memory)

5+M-VFO : set up ch.80-89 to accept any memory data

RX/A : Turn ON/OFF SUB receiver marker on SM 230 Monitor in 100 kHz/250kHz and 25kHz sweep mode.

IC+COMP : stop transmit if Ic exceeds 1,7 A. Power output limited to 10 Watt

8.83 + RIT : Both 8.83 MHz and 455 kHz IF Filters are selectable on transmit. Each memory channel is also capable of storing this setting.

Memory protect: Cutting D 129 on control unit protects memory contents from being erased.

Write protect: Cutting D 18 on Control Unit write protects all memory channels.

from Hanno DG8JZ


Allows sub-receiver to be on different band than Main receiver.

TS-950 function Believed to work in the 950sdx

This is a Power On function mod.
Start with radio turned off.
Hold down buttons SUB, M/S, RX/SUB while turning on the power ON. Now you can listen to 15M on sub-rcvr with Main rcvr on 20M. or any other band or visa-versa. Both receivers will be in the same mode USB, LSB, CW etc.




by and NA1A

Note: This mod is not required to achieve the full transmit response of the 950SDX.

  1. Turn off the 950SDX.
  2. Turn on the 950SDX while pressing and holding the
    "Scan" and right "M.CH" button simultaneously.
    Note the new "OFF/ON" status in the sub menu display.
  3. Menus 0 - 5 are shown below...
  4. Select menu "01" and turn On. [Use the 1 Mhz UP/DOWN button and set Memory 01 to ON]. This enables the I.F. filter select during transmit.
  5. Hit CLR to save this new setting and exit.
  6. To remove the secret menu, turn off the 950SDX, then while pressing
    the "Menu" key, turn On the 950SDX. Then press the "Menu" key again.
  7. For best fidelity, select the "6k" 8.83MHz filter select during transmit (Factory default). Do NOT bypass the 8.83MHz I.F. during transmit because the frequency response and power output will not be as good! This mod is only handy for selecting narrower transmitter bandwidths (i.e. 2.7k) for DX or other narrow band applications.








Product I.D. (Yours may differ)




Turn On - Enables 8.83 MHz I.F. Filter TX Bandwidth Selection




RBK/ABK forced off mode (Test Mode) Keep Off




2 Tone On/Off (Test Mode) Keep Off




Transmit notch filter On/Off (Leave ON !)




Power On "Hello" Display (Only works once?)


Now your TS-950SDX can transmit in different filter independently from the receive filter settings.

73, Duke - NA1A


Subject: [KenwoodTS-950SDX] Digest Number 22

Date: 11 Feb 2004 10:54:45 -0000







Topics in this digest:


      1. Re: TX Filter Selection

           From: "aa0potom" <

      2. Re: Re: TX Filter Selection

           From: Tom LeClerc W1TJL <

      3. Re: Re: TX Filter Selection

           From: Berry W6EZ <



Message: 1

   Date: Wed, 11 Feb 2004 00:57:52 -0000

   From: "aa0potom" <

 In the TS-950SDX, you can transmit through different filters. The

 way how to do this is as follows:

 1. Push and Hold M.CH and SCAN button, then turn the rig on.

 2. Select Memory 01 using the M.CH/VFO.CH knob.

 3. Use the 1 Mhz UP/DOWN button and set Memory 01 to ON.

 4. Hit CLR to save this new setting and exit.

 Now your TS-950SDX can transmit in different filter indecently from  the receive filter settings.

Subject: Re: TX Filter Selection


 A couple of questions – Has any one tried this "modification"?


 it work?





What is it supposed to do?




  I would have thought that the transmit and receive filters were already independent (but what do I know, I am an operator, not a tech).





If this apparently undocumented menu selection does work,



is there anything to be gained by using it?



And finally, assuming this "modification" works and that there may be some reason to use it, would there be reasons not to use it?




It seems that if it were a useful adjustment, then it would be covered in the instruction manual (if it is, I haven't found it).






















73 de AA0PO  TOM



Message: 2

   Date: Tue, 10 Feb 2004 17:20:36 -0800 (PST)

   From: Tom LeClerc W1TJL <

Subject: Re: Re: TX Filter Selection


I have tried this and I don't get a menu by doing this on my SDX.  First, there are two M.CH buttons - I have tried the first button and scan and what i get is the radio scanning the memory channels depending on which button I release first after turning on the power or nothing at all.  If I use the right hand M.CH button and scan the radio comes up with 1.100.16 in the frequency area of the display and a lowercase "on" in the lower right hand corner of the display.

 When in this mode nothing can be done - I have to power it down – no buttons have any effect.


Am I doing something wrong??  Thanks in advance for any help...

Tom LeClerc, Amateur Radio Station W1TJL

  (past calls WB1CBY, /VE8, /VE1, /VO8)






Message: 3

   Date: Tue, 10 Feb 2004 23:18:28 -0800

   From: Berry W6EZ <

Subject: Re: Re: TX Filter Selection


I just tried it and it worked on my SDX. Held the right side memory button (tx)

After setting to "on" it works just like the 850 when this option is turned on.

Hold down PTT while making filter selection.

If selection is not the same as your rx setting you will be able to see it the filter selection indicator toggle back and forth when you hit the ptt.

not too shabby.

 Berry w6ez












  1. Turn off the 950SDX.
  2. Turn on the 950SDX while pressing the "ENT" key.
  3. Set menu number 04 to ON.
  4. Press the "ENT" key to complete this programming.
  5. Turn off the 950SDX.
  6. Turn on the 950SDX while pressing the "MENU" key.
  7. Set menu number 73 ("Fil Sel") to OFF.
  8. Press the "MENU" key to complete this programming.
  9. Press the "455" FILTER button until "250" shows in the window.
  10. Turn off the 950SDX and remove bottom cover.
  11. Locate the optional "YG-455CN" empty CW 455kHz i.f. Filter slot.
  12. Place a jumper wire from pin #2 to pin #2 to make a short across these pins to complete the 950SDX 455kHz 250 i.f. circuit. (Jumper will be a diagonal connection)

    Note: You may want to turn on the 950SDX at this point to confirm that you have the correct pins shorted. You will here the receiver come alive if you have the correct pins shorted. Otherwise, you will hear nothing. Make sure you have selected the 455kHz 250 FILTER from the FILTER select on the front panel. Also, the jumper will be a diagonal connection as the pins are in reverse from one side to the other.
  13. Replace cover and turn on the 950SDX and enjoy an extended SSB receiver response of about 7kHz instead of 6kHz while in the 250 FILTER position. In the AM mode, the response will be
    considerably wider, about 12kHz as opposed to 6kH.



Preventing final FETs failure

author: Tony, I0JX

My suggestion is to replace the two 22-ohm 0.5-W resistors marked R15 and R16 with carbon-type resistors of same value but higher power (e.g. 1 W).

Those resistors are located in the "Final Unit", not too far away from the final Field Effect Transistors (FETs). Replacing them is fairly easy. The rationale for the proposed modification follows.

I have my TS-950SDX since about 13 years. In year 2004, the final FET marked Q4 2/2 unexpectedly failed, with no apparent reason. A circuit check showed no problem whatsoever, therefore I attributed the failure to an occasional fault, and I then just replaced the faulty FET with a new one. But in year 2005 it failed again. Then, before replacing the FET another time, I performed an very accurate circuit check.

With the aid of a magnifying lens, I realized that resistor R16 had got a bit deformed at its center, taking a "barrel" shape. After carefully inspecting and testing that resistor, it was evident that it had overheated and that it was subjected to an intermittent contact.

At times when that R16 opens up, the RF drive voltage on FET Q4 2/2 gate grows up a lot, causing its failure. Evidently that resistor is undersized, as it does not withstand the applied RF drive power.



Front-panel Sidetone Level Control for theKenwood TS-950S (may also apply to TS-950SDX)

de K0ZL 2/2/05







Detailed Manual by International Radio.

The detail on pre-amplifier circuits looks especially useful.











Zl4AI question:: In your website I see you now use an FT100MP MK5. How does the 950sdx compare with the FT100MP?

The Field is more "clever"...More "bells and whistles". The 950SDX is a better mechanical build, and is easier to get at to fix etc..older technology. There's little between them on RX performance..Both excellent when they have decent filters. Maybe the 950 is a little quieter on RX. On TX, I'd say the 950SDX is better. Always great SSBTXaudio, and nice clean CW....unlike the "clicky" MP and Field. I've done 4 mods to my Field, and MP (W8JI click mod, NB mod,AGC mod and added a roofing filter). None needed on the 950.


Bud Hippisley, K2KIR
Wed, 03 Mar 2004 22:34:25 -0500

From: "Donald E. \"Buck\" Stiles" <
I am soliciting constructive comments regarding the Kenwood TS-950SDX.  If you have an opinion on this radio, I would like to hear it, good, bad or indifferent.
I have a TS-950SDX  --  actually, I have two of them.  Here's why:
1.  I'm partial to Kenwood's ergonomics, starting with the old TS-180, and running through the 
TS-930, TS-940, and TS-850 to the TS-950SDX.
2.  Like the 930 and 940, it has really great QSK CW, without shortening of the first dot.
3.  The receiver synthesizer is very clean.  (Same generation as TS-850.)
4.  I wanted dual receive.  (Note -- the sub-receiver is meant to be used only on the same ham 
band, not cross-band.  Although you can get the sub-receiver to operate on a different band through 
a "secret" menu item, it has lousy sensitivity there because it's still using circuits tuned for the main band.)
5.  It has the Quick Memory function in a 5-tall push-down stack.
6.  You can independently select TX and RX frequency sources:  VFO A, VFO B, and MEMORY.  
I run my CW traffic nets by putting the TX on a MEMory; then I can tune around the net frequency with 
the main tuning dial whether I'm transmitting or not.
7.  It has a separate RX antenna input for bringing in Beverages, etc.
8.  The built-in antenna tuner has memory, even tho the manual doesn't mention it.  So when you 
change bands, the tuner automatically sets itself up properly for the new band/frequency.  
In contrast, the 940 tuner has no memory.  Whether using an amplifier or running barefoot into different 
SWRs on the different bands, this feature alone is a hidden "jewel".  
9.  The TX audio is typical excellent Kenwood communications audio.
10.  The CW waveform is excellent, and the rise and fall times are menu adjustable to prevent key clicks.
11.  It has nice peak-reading hold circuits for the metering LEDs.
12.  It has a built-in keyer and three built in CW messages.  By adding the voice synthesizer option, 
you can also have three built-in voice messages, or two built-in messages and a continuous off-the-air 
recording loop for convincing yourself of a callsign, etc.
13.  It uses a conventional hi-IF / low-IF selectable filter scheme to obtain excellent intermod performance.
  Some people replace the stock Kenwood filters with International Radio filters to get steeper 
skirts.  I have not felt the need to.  
14.  It has some DSP functions, most of which I set once and then "forget".
What don't I like?
1.  It doesn't have a standard d'Arsonval meter.  (pardon my spelling.)
2.  RF coming in the RX Antenna input from, say, a Beverage wire, can cross-couple into the TX stages during 
transmit.  If you use a separate RX antenna, you should add some external circuitry to ground the RX Ant input 
during transmit periods.  (A number of other kinds of rigs have been reported to have the same problem, 
I should note.)
3.  It sometimes needs a pre-amp on 10 meters.
4.  The RX audio peaking filter on the 940 does a better job than the DSP filter on the 950SDX.
5.  Unlike the 940, the CW pitch cannot be set below 400 Hz.  I much prefer 300-350 Hz for separating 
stations with my ears.
6.  You have to use the outboard RM-1 remote control (or a homemade equivalent) to run the three 
CW/SSB message generators.  Unlike the TS-850, there is no way to record or start the messages from 
the front panel.
7.  The RX/TX transition when monitoring CW in QSK mode is not as "smooth" as on the 940 or 930.  
(There's more evidence of gain pumping.)  This is a local monitoring issue -- there's nothing wrong with 
the transmitted signal -- and I've gotten used to it.
8.  The CW sidetone monitor level is only adjustable on the underside of the radio, and does not track 
with the main volume control.  (I modified mine to allow me to at least adjust it with the front panel 
MON control.)
9.  Compared to the 940, the RIT/XIT tuning is too slow for me (i.e., too many turns to go a kHz).  
On the other hand, it's far better than that of the 850, which is not an optical encoder and hence has no 
"push to clear" button, and which only goes 1.2 or 2.4 kHz.  For contesting, the 850's RIT was a deal 
breaker for me and the reason I bought my first 950SDX instead of two separate 850s.
10.  The set-up method for putting one VFO on a DX station's frequency and using the sub-receiver 
and second VFO to find and transmit where the DX is listening is cumbersome at best.  I finally wrote 
myself a "crib sheet" on a 3 x 5 file card that I keep near the rig.  I now can do it from memory, 
but it took me a long time.
11.  In general, the operator manual could be better.
Fundamentally, the 850 and the 950SDX represent the "next" generation of receiver performance from Kenwood 
compared to the late model 940s.  I don't think subsequent Kenwoods, such as the 870 and 2000, are as good 
as the SDX.  By the way, my two SDXs are near the beginning and the end of the production period for those 
rigs; there's virtually no difference in their performance, unlike the many significant synthesizer changes 
that occurred during the 940's production cycle.  
There was a time, shortly after getting my first SDX that I thought I would never completely leave my 940 for 
the SDX.  But today, if I could keep only one radio on the market, new or used, it would be the TS-950SDX.  
I have friends who believe the Icom 781 or the Ten-Tec Orion are better receivers, and I've used both of those.  
But to me, because of the ergonomics, my SDX is more fun to use.
Bud, K2KIR 






RFI Susceptibility


AA5CH on December 30, 2004

First noticed oddity when connecting the W2IHY EQ to the 950... low  level hum...greatly reduced it by moving the EQ away from the rig. Also noticed that tapping the mic connector with the rig in TX produces sound similar to tapping on a live mic...I (perhaps mistakenly) have called this "microphonics?"


Rig appears to be unusually susceptible to RFI...running non resonant antenna w/balanced feedline at times so RFI in shack is no great surprise; however, using the same mic, same antenna / tuner setting / amplifier setting, my TX audio is clean from a TS2000 sitting next to the 950. I was even able to drive the rig into RFI with no microphone connected by turning the processor on and all the way up.


Found some improvement by disconnecting the 950 from the station ground bus and installing an MFJ artificial ground. No problems noted when running a resonant antenna or dummy load.


I'm thinking that there is a design quirk in the mic pre amp stage that results in the preamp being at a different ground potential than the rest of the rig...or perhaps there is a poor connection or failed component in that section?


Been doing some research but haven't found any reports of this being an issue or found any technical bulletins that refer to this phenomenon.


With the same operating conditions, it strikes me as odd that the TS2000 would be clean when the 950 is RFI plagued, and that RFI is present in the audio WITHOUT a mic being connected to the radio since mics and mic cables are typical entry points for RFI.


Brad AA5CH




ZL4AI has on and off had terrible RFI distortion, when running MC-60A mike, and SB 221 amp.

Station and amp all well grounded without ground loops.

RFI occurs (and only sometimes) when my hand touches the metal body of the mike stand.

No solution yet. Wondering if solving the Terrible audio hum has helped solved this. Will let you know, when more field testing is completed.











Audio Modifications

Serious Audio modifications can be found at WZ5Q TS-950sdx Receiver Mods


These certainly look interesting. The basis of before and after change is well recorded. What is not stated is why these changes achieve an improvement.

I am not knowledgeable in Audio or HI-FI. Possibly it is common knowledge in audio circle there why a tantalium capacitor is better or worse.

Problem I have is, that while these modifications may well be worth while, I would suggest any reader learns more about HIFI to understand what the advantage of the changes promoted really are.

Having said that when one hears good HIFI audio on the air, it certainly sounds like it is a significant improvement.