1. Kenwood Serial Number Decoder

TheTS-850S Repair PageMaintainedby Larry “Tree” Tyree – N6TR – Boring, OregonLast updated on 19-March-2019This page has moved to a new home on kkn.net after many years onjzap.com.RIP “JZap” – K2MM – John M ZapisekMay 25, 1951 – August 18, 2012Please feel free to link to this page, but please do not copy theinformation here. It is updated frequently (well if you measure time witha calendar).The Kenwood TS850S Amateur Radio Transceiveris a very popular radio. It was in production from 1989 until around 1996 whenthe TS870 replaced it. This page is dedicated to helping 850 owners keep theirradios on the air. This is starting to become a bigger and biggerchallenge as time goes on.I would like to thank all of those who haveprovided information used on this page. If you have other information thatwould be of interest, please pass it along to me and I will add it to thepage. My e-mail address is tree at kkn.net.First– The BAD NEWS!!One of the biggest issues with TS850S repairis finding parts.

I am sorry to say that getting new parts is almostimpossible now and likely the only way you are going to fix your radio is tofind a donor radio that you can swap modules with. However, there is onepart that is really a big problem for those who have some of the first year’sproduction. This is the four YM6631 DDSchips on the CAR board. This is a custompart made by Kenwood for the radio.

Kenwood Month/Year of Manufacture Calculator. Laurie - G6ISY developed the method of calculating the manufacture date.You can find his original work in the files section on the Yahoo group for the TS-2000. TS-2000's (Including the X model) in the serial number range 810xxxx. Located on top or back of it, and call Kenwood direct with the serial the serial number, they have all codes on file, they can help. Here are the numbers Kenwood Australia - 1800 126 659.

Ifyou have these older chips – it is only a matter of time before they will selfdestruct. Kenwood realized they had aproblem and fixed it in the YM66312 version of the chip. However, there was no extended warranty forthis problem – and sadly – there are no longer any of the new chips availableto replace the old ones.The net result is that if you have a TS850 with the older chips – youare going to have a hard time keeping this radio on the air (or getting it backon the air if you have had issues).

Overthe years – many people have contacted me via e-mail saying that they arehaving weird problems with their radio. My first question is to find out if the serial number starts with thenumber “2” – and if so – check to see ifthey have the old DDS chips. Often –they will have had one or two of them replaced – but the other ones are nowacting up and they are out of options.These chips do many different things in theradio – from generating RF frequencies used in the mixers – to even generatingthe side tone when sending CW.It is really sad that Kenwood is not doing abetter job standing behind their radios. It is due to this situation that I will never buy a Kenwood radioagain. You can find people at Kenwoodwho are sympathetic – but they have been unable to convince management toproduce some more of these chips.Sometimes – you can find some on ebay. I think I saw four of the new chips sell forover $300 a couple of years ago.

I havesold a CAR board with four new chips on it for over $300 as well. The new chips DO NOT FAIL!! This is a clear indication that something waswrong with the design of the older chips.Some people have parted out their TS850 – butoften this due to the fact that they have the old DDS chips and have givenup.NOW – for the good news!!

I was hoping someday, someone would design a replacement CAR PCboard that used modern components – and that has finally happened!! You can find them for sale on ebay. Useful Links- Agood collection of 850 mods. Of two mods I have done. One isan RX antenna input and the other is enabling the MONI control to adjust the CWsidetone level.- You can purchase some parts for your radio on-line. Please be preparedto pay top dollar for parts however. They do NOT have the DDS chips availableany more.- Clif can fix your radio if you can't.

Check out I am happy toreport that rumors of Clif being out of business are now incorrect.- Lots of good information here.- a good place to ask questions.- By request for those who can't get a copyof the service manual.–More service manuals and documentation.A Russian with a.PDF copy of the service manual (without the board drawings Ibelieve). 7 Megabytes.A new with.PDF copy ofthe service manual AND board drawings. (thanks 9H1FQ). (N6TR)This is the typical symptom from the most common component failure I haveheard of in the 850. The cause is that some of the band pass filters on the RFboard are always enabled by the 74LS145 decoder chip. You can verify this byusing a voltmeter and seeing if one of the outputs from the chip is always'low' (near zero volts).I would suggest putting a socket down on the board for this IC - so if itever fails again, you can replace the part quickly. This will require removingthe RF board (which is the one underneath the radio with the shiny shield onit).

The IC is under this shield.I have received a comment that Kenwood often replaces a MI303 diode whenreplacing this chip (thanks K5TSQ). There is mention of a modification on theKenwood site that might also help eliminate this failure. Check out the for more information.I believe this failure might be a result of a high RF voltage beingpresented on the receiver input. I do think one or two of the failures I haveseen might have been caused by transmitting with full power with a differentradio with antennas that were close. It has also been suggested the 47K ohm DCinput resistance of the receiver could easily allow nearby lightening hits toproduce a high voltage.Perhaps putting an inductor on the RX antenna input to ground would help asexplained as follows:Prevent Static Charge Buildup (K0ZL)Remove the surge absorber tube on the small pc board connected to theantenna connector, (remove top cover of filter unit, top of rig, rear-center,to get to it). Obtain a 1-2 milli-henry pi-wound choke (one of the bigoldies-but-goodies), and tack solder the surge absorber across it.

Re-installthe assembly where the surge absorber was. You now have 2 ohms toground DC, and much harder to develop high static voltage. The part number isHammond 1535B, 2.2 mH, from Antique Electronics (www.tubesandmore.com). Thesurge arrestor is DSA301LA.9H1FQ warns: “I had an R7 vertical connected to my TS850.On a clear blue sky day, I saw a flash at the back of my rig. At the time, Iwas unaware that I had a DSA301La gas filled protection tube. Later Ifound, that the R7 vertical has a choke, which bypasses the whole matchingunit, as a protection.

The choke was open circuit! I would think twice, beforereplacing the gas filled tube with a choke, as you mention on your website.”. Inmorse code over the speaker (N6TR)The “UL” indicates an unlockedcondition with the frequency synthesizer.This failure might be temperature related - and possibly show up more oftenwhen tuning the VFO in specific places (around 1800 - 1850 kHz is one place Ihave seen it fail). This is probably the DDS chip on the carrier board thatproduces the VFO frequency.

The CAR board is under the bracket that would holdthe voice memory board if you had it (under that door on the top of yourradio). Remove the four screws that hold the bracket and find the CAR boardwith the four big chips on it. You can put a scope on the PLL-1-DL01 output andwatch the output voltage as you tune around. On a functioning board, the outputlevel should be pretty constant as you tune the VFO through a 500 kHz segment.If the output changes a lot when the VFO jumps from one frequency extreme tothe other, then the failure is probably the IC1 DDS chip. They cost $28 andwill require you to have the right equipment to work with surface mount VLSIICs.One step you should take first is to make sure all of the connections to theCAR board are good.

Remove all of the cables, and reseatthem. (N6TR – NR1DX)I had this problem with one of my radios after taking it to Louisiana forthe Sweepstakes. The signals on 20 meters all sounded raspy - andbroad. At first, I thought it was something wrong with the transmitter ofthe other station, but when all of the signals on the band had the same problem,I knew it was my receiver. I believe my transmitted signal sounded asbad. It seemed to be temperature related and in extreme cases, the LO1output from the PLL board was going away.And then Dave, NR1DX, hit the nail on the head with this:I just finished fixing the second TS-850 in my career with thisproblem.particularly symptomatic is the raspy sound which gets worse as theunit heats up. In both cases TC1 on the PLL board needed only to be adjusted sothat TP2 reads 5.0v.

(See the service manual page 98, step 8). The littletrimmer cap TC1 inside the VCO-2 can has been documented as getting flaky withtime. On the first radio the problem occurred at about year 7 resetting the capcured the problem and the radio ran fine for another year without incidentbefore I sold it and upgraded to a TS-950SDX.I recently came on a bargain ($550) TS-850SAT (10 years old) which wastoo good to pass up (including the a 500HZ and 270 Hz CW filters and a DRU).

It had this same problem only worse in that after setting the cap theunit would play fine. For a while, then drift back into the same oldproblem. I then replaced the cheap Kenwood trimmer cap with a glasspiston trimmer cap which so far after four hours is stable as a rock. Ill sendyou a picture of the mod ( if you want it) as I had to drill a hole in the sideof the VCO-2 can to mount the new trimmer cap.So check your problem radio's PLL - TP2 when it gets raspy, I'll bet itis no where near 5Volts, the setting is quite critical.When I checked the voltage on TP2 (located near the front of the board rightnext to the smaller shiny box), it was around 4 volts. I adjusted it upto 5V, and things sounded worse. That was until I removed the lead tothe DVM (it was acting like an antenna and picking up all sorts of junk).After that, the radio sounded like new. When I thanked Dave, I got thisin response:Don't thank me.

Thank Cliff at AVVID he is the one that clued me inthe first time three years ago. The guy is amazingandYou will see the little piston cap on the left of the VCO2 can.

Thelittle melt from the soldering iron on the edge of the little blue plasticthingy was an 'aw- $#!^', in trying to clear the holes in the board.Didn't hurt it electrically.To do this you have to remove the whole VCO2 enclosure there are about 5 placeswhere the can is soldered to PLL board plus three wires. If you have never usedsolder wick now is a good time to learn.

Removing the can is almost asdifficult as brain surgery but still not as bad as changing one of the DDSchips. (from W9PL/7)My 850 was purchased new in 1993. It was repaired twice under warranty forthe same symptoms. The symptoms (to make a long story short) involved aninoperative receiver in all modes other than FM. The initial failure occurredafter a few months of use, in 1993.

The second failure occurred after only 5hours of operation following the first repair action. However, since the secondrepair action, it has worked just fine and I am very happy with the radio. Thefirst time they repaired it, Kenwood replaced a VMI308 diode and a 3SK131(M)FET (Q15) on the IF Unit. Q15 is the last of stage of IF AMP preceding the SSBDemod. The second time they repaired it, they replaced the same FET (Q15) onthe IF Unit. I suppose they had a 'bad' run of Q15 FET devices atthat time.No receive (N6TR)I had a friend send me his radio with this symptom.

I noticed when Iturned the radio on, there was an oscillation that I could hear coming from theRF board. I found it on a bunch of signals - and measured it around 11kHz.

I looked at the 3rd mixer of the receiver (which is on the IF board)and saw the 455 kHz signal going into it just fine - and nothing coming out ofit. You could inject an audio signal there if you wanted to see if theaudio chain was working okay.

I also didn't see anything going into themixer.My attention shifted back to the front end - where I saw all of the strangeoscillations. I looked for the signal coming into the first mixer - whichis a pretty high frequency from the LO1 signal - buffered by Q28. Icouldn't find it. I checked the two diodes that steer the output of Q28to either the receiver or the transmitter - and saw it working FB for thetransmit condition, but not so good for the receive condition. The biasfor the diode comes from the signal RXB - which should be around 8 volts whenin receive. This is generated on the IF board on one ofthose little modules that stand vertical on the board.

Without thisvoltage - there is no way the receiver is going to work. I could jumperthe RXB signal to 8 volts and make the oscillation go away. My next stepis to see if doing this makes the receiver function again. I will probablyreplace the components on the little pc board to fix the problem as Kenwoodprobably wants too much money for the replacement board. Three is onlyabout 10 components on the board - and they should be cheap to replace fromDigiKey or Mouser.Well, it turns out the little board is probably okay.

I found that theproblem was the TXB signal was not going all the way to ground when in receive- which kept the RXB signal from turning on all of the way. If Igrounded the TXB signal, the receiver came to life. I removed the module- and found that both RXB and TXB were at ground. However, if I pulledRXB up to 8 volts, TXB came up to about two volts. NOT GOOD!There is obviously something leaking RXB voltage over to the TXB signal.My next step is to try and find where the leakage is taking place.Probably a diode somewhere has turned into a short circuit.I swapped RF and IF boards with a good radio and isolated the failure to theRF board.I checked all of the diodes on the RF board with a meter.

There were a fewthat had funny readings, but they were the same as my good RF board. (N6TR)It is possible that one of my DDS chipfailures was really due to a poor solder connection. I noticed when replacingthe chip that there wasn't a lot of solder on the IC pins.

I was able to reusethis chip on another board and it came up and worked fine. The followingcomments are from an ex Kenwood service person: The history we were givenregarding the solder quality is that amateur gear is a very low priority, lowquantity production run at Kenwood. The PCB blanks are all made at a plant atone time for the estimated life production run of the rig. Then they areshipped to a plant where maybe 6 months or even years later the PCBs are usedfor a small run of the units.

Kenwood Serial Number Decoder

This plant is on a coastline and the boardssuffer from salt air corrosion problems, so the solder does not wet properly. Ican believe that story, but they still suffer from very poor QC with regard toinsufficients, cold solder, and lack of eyelet properly done before solderingon the older PCBs. Kenwood has service bulletins out on some boards, where theypoint out 30 to 60 feed through for shotgun re-soldering of eyelets with a barewire fed through the eyelet hole when re-soldering and then clipped off. Radio Fails in FM Transmit mode –microphone amplifier not working (CT2HMX)I saw the Board X59-3000-03, FM mic amp and all components were okay. I puta 1 kHz tone, 5 mv, into the the mic input on the front of the radio and sawthe signal on C630 on the RF board (X44-3120-00). I did not see the signal onthe collector of Q609 however.

The hfe (beta) of this transistor was very lowand I replaced Q609 (2SC2912A) on RF board and the problem was solved. The oldtransistor wasn't bad - but the hfe gain was very low and caused the failure. Replacing Rotary Encoder (DJ3TZ)I recently had a problem with my 850 which I could fix myself and would liketo share this information. It concerns the rotary encoder that transforms anymovement of the main frequency dial into digital pulses.

The part in questionis a COPAL RMS20 encoder.For a long time, my Kenwood TS-850 had the problem that while turning the mainfrequency dial, the frequency would stop changing with the last digitjittering. For several years, the problem occurred so rarely that it did notreally hinder operation, and I saw no chance to locate the problem.Recently, however, the problem became more serious, making the radio almostuseless. Using the 850's service manual, I was able to locate the encoder andits connection to the radio's main data bus.The encoder has two data outputs, A and B. Both carry digital signals at 5Vlevel. Its frequency depends on the rotation speed and the signals differ inphase to allow for clockwise/counterclockwise detection.

Together with myfriend Theo, DJ9PK, I observed these signals with an oscilloscope. One of themvanished whenever the the frequency stopped changing.Taking a look into the encoder, we tried to locate any kind of mechanicalproblem, perhaps a little bit of dust, but there was none. The encoderconsists of a magnetized wheel and an magneto resistive Hall sensor, inaddition with some electronics. Checking the signals from the sensor revealedthat is analogous. It consists of a voltage of approximately 2.5 V DC plusapproximately 80 mV AC when turning the shaft.We found that the amplitude of the AC voltage strongly differs while turningthe shaft. The reason is perhaps that the magnetic field produced by the wheelis not constant, but seems to depend on its position towards the Hall sensor.The amplitude seems also to depend on other, unknown factors.The PCB inside the encoder has an IC that obviously works as a comparatorand digitizes that input.

Checking its 8 pins revealed that two carry the inputcoming from the sensor, two carry the digital output, and two pins areconnected to reference voltages. These reference voltages can be adjusted withtwo variable resistors on the left and the right of the IC.Turning one of the resistors fully into one direction causes the digitaloutput to become constantly low or high, respectively, because the referencevoltage then is always higher or lower then the sensor signal. Within a rangeof 10 or 20 degrees, the comparator works as intended. I suspect that thereason for the occasional failure was that the amplitude of the AC signal wassometimes below the comparator's reference voltage, thus causing the output tostay high or low.Rotating the shaft by hand but at a constant speed and observing the digitaloutput on the scope allowed us to adjust both resistors so that encoding nowworks fine.Here is the pin layout of the IC:1 Output B2 Reference voltage B3 Input B from sensor4 Gnd5 Input A from sensor6 Reference voltage A7 Output8 + 5I hope this information will be helpful to you and others.

(PA0RLS)Beware of C1 on the CAR-UNIT: If it starts leaking (I mean fluid coming outof it) then you may expect all sorts of crazy things. Most common are: RXis deaf and/or the TX led is on during receive. Monitor the TXB line duringreceive: It MUST be 0V. If not the problem above may be the cause, as the +from this cap. Leaks to TXB! Replace C1 by a normal (not SMD/metal can)electrolytic capacitor: 100 uF / 25V will do. You may see that the fluid fromthe old C1 is etching the PCB and in one case I had a hole burnt in the PCBjust under C1.

Replacing ALL other 10 uF elec.caps is strongly advised, as theyALL start leaking fluid that ruins the PCB. Remove them all and CLEAN the PCBbefore putting new caps on. Open the little hatch on top of the radio.

Locate VR501, VR502.2. While depressing F. LOCK, turn the transceiver ON.3. Control until MENU 00 is displayed.4. Turn the power control all the way down.6. Push the SEND switch.7. Make a slight adjustment to VR501 to make your voice higher or lower whilespeaking into the mic, listening to yourself in the monitor.8.

Put the radio in USB.9. Make a slight adjustment to VR502 to make your voice sound higher or lowerwhile speaking into the mic, listening to yourself in the monitor.10. Put the SEND/RCV switch back to RCV, and then press CLR.11. Listen to on-the-air signals on both USB and LSB to see if additionaladjustment is required. Open the bottom hatch of the TS-850.2. On the IF unit, locate VR8 and VR9 (near the little Murata filter).3. On the TS850: PROCESSOR OFF, MIC GAIN MIN, FREQ 14.2, MODE USB, POWER MIN.4.

Construct an RF voltmeter by sticking a silicon diode, such as 1N914 intothe antenna socket. Connect a sensitive DC voltmeter between the diode andground.5. Push the SEND switch on the TS850 and adjust VR8 and VR9 for minimumindication on the voltmeter.6.

Make sure that BOTH of these controls are going through minimums. It ispossible to get so far off on VR8, that VR9 has no effect.7.

Check that LSB is ok also.8. For the best final measurement, take a piece of insulated wire, bare oneend, and stick that end into the antenna socket of the 850. Bring the insulatedwire NEAR the receive antenna connection of a second receiver tuned to thecarrier frequency, and make fine adjustments to the null, with the POWERcontrol set at MAX.

Of course, do not connect the second receiver directly, incase your hand slips while you are making the adjustment! I just wrap theinsulated wire around the center pin of a PL-259 connected to the secondreceiver. (I7ALE)The problem was that when you switched the radio on, in would go in'SEND' status, in any band or any mode. The set was perfectlyworking, in the 'Send' condition, but no way to have it go back to'receive'.After checking out all the most likely 'areas' for this problem(microphone port, SEND/REC push button, keyer input, etc.), further analysis ofthe digital unit X46-3080-A4 and in particular of the IC2 processor revealedthat pin 5 of IC2 was LOW, as it should be when the rig is in the SENDcondition.

This pin is also connected to the SS line, going from IF UNIT to thedigital unit and to other boards, among which the BK SW, which is an interfacebetween the CW KEY port and the IF UNIT. It was discovered that the problem wasdue to a short between the collector and emitter of the 'digitaltransistor' Q3 in the BK SW board, which short forced the SS line to LOW.Replacing the damaged transistor (DTC 124EK) solved the problem. Noise Blanker Performance Improvement (WA3REY and KI6MZ via N3US)There was a lot of interest about the noise blanker mod posted here a weekor so ago so I'm passing along my results. After performing the mod (copiedbelow) the noise blanker in my TS-850 reduces line noise from an S8 on 10 meterAM to S3 or less. This is much better than before the mod.

On SSB, the noiseblanker reduces noise several S units, but not as dramatically as on AM. Themod is 'simple': Remove C618 and C619 from the circuit. But findingthe chip caps is next to impossible without using the Service Manual. Listmember Rick, KN3C, located the chip caps - they are on the solder side of theboard - then removed them for me. Again, don't try the mod without the ServiceManual because the two caps are unmarked. 73, Tom, WA3REY-Mod follows-Hi Dave When I took delivery of my TS850 and used it along side of myTS940.the 850 was noisy and turning the noise blanker on had no effect.someof the noise was radio noise and some was power line noise.the noise blankerin the 850 had no effect on the power line noise.I sent the radio back toKenwood.they said it operated as they wanted it to.i.e.

SO-2 Replacement (N3BA)The SO-2 unit is no longer available, or at least is reallyexpensive. I have been able to make an aftermarket SO-2 from commerciallyavailable parts, and the performance has been astounding. It really settleddown my drifty 30 mil s/n TS-850, and I made one for a friend who swears by it.I've built and sold 6 more of them for $75 apiece. If you want to post a linkto me on the page, I would build one for anyone who needs it. You can reachBob, N3BA at robertan at cfw dot com. (K6LL)Along with a terrible burning smell coming out of the fan vent whenever theradio is in transmit.

When the top cover is removed, the smell seems to becoming from the left front side of the radio. The following failure occurred onboth of my TS-850's within a six month period.Problem: The problem is that C1 on the Carrier Unit, X50-3140-00, hasfailed. This board is the second board down in the 3-stack of boards on theleft top side of the radio.Solution: Unscrew and remove the shield that covers the board.

Access to theunderside of the board is not necessary. Inspect C1 for signs of burning. C1 islabeled, and is the largest of the electrolytic caps on the board.

If damage isverified, remove C1 by heating its two small mounting tabs to unsolder it fromthe board. After C1 is removed, make sure that the circuit board trace thatruns underneath C1 has not been blown open. If so, repair it by jumpering withwire. Replace C1 with a conventional 47uf 35vdc radial lead electrolyticcapacitor. I used one from Radio Shack. Mount the capacitor in a couple ofconvenient copper holes that are adjacent to where the old capacitor leads wereconnected.

The plus side of the cap attaches to the trace that goes to L1(looks like a resistor, it's labeled), and the negative side goes to ground.Dave Hachadorian, K6LLYuma, AZ. Quick Dial Calibration Check (K6LL)1. Tune the radio to 10Mhz, so you can hear WWV.2. Press the 'tune' button on the radio (keypad #7).3.

Set vfo A to 10000.10 KhZ.4. Set vfo B to 9999.90 Khz.5. Flip back and forth between vfo A and B.

On both, you should hear a low toneof about 100Hz, just off zero beat of the WWV carrier. If the tones are notequal in frequency, adjust TC-5 on the PLL Unit, as follows:TS-850 Quick Dial Calibration6.

Remove the TS-850 top cover.7. There is a three-stack of boards on the left side of the radio. On the leftside of the lowest shield, there is an elliptical cutout. Peek inside, and youwill see the screwdriver-adjustable pot TC-5.8.

Make small adjustments to TC-5, and repeat step 5 above until the two tonesare exactly equal in frequency. Vox Gain Improvement (N3BA)Bob, N3BA offers this modification to improve the VOX gain:I have a link to another great mod that applies to the TS-850.

I've beenusing a Heil HC-5 mic cartridge on my '850 that sounds great but has too littledrive to trip the vox properly, even with vox gain all the way up. I performedthis easy mod on the vox daughter board (located on bottom of rig, right rearside with knobs facing you) marked 1080-01 on the non-component side. Same voxboard is used in the TS-950, and the mod posted at great pics showing how to do it. Now I have plenty of vox gain for theHeil, and you can always turn it down enough to use an MC-60 or other mic.