Kenwood TS-850 (1989–1996)
A well-loved HF transceiver whose reputation took a hit from four custom chips that Kenwood couldn't or wouldn't replace.
Overview
Ask anyone who ran the HF bands in the early '90s and they'll know the TS-850. Kenwood built this amateur radio transceiver from 1989 until around 1996, when the TS870 took its place in the lineup. It was a very popular radio, the kind that showed up in shacks everywhere and stayed there. Universal Radio positioned it as a competition-class transceiver designed for the serious radio operator. The specs backed that up: 100 watts of output (40W on AM), coverage from 160 through 10 meters including the WARC bands, and worldwide marketing with provisions to transmit between 1.625 MHz and 29.999 MHz.
The naming is simpler than it looks. The "S" suffix on so many examples, as in TS-850S, is a regional and marketing variant of the same base transceiver, not a different machine. Collectors and operators treat TS-850, TS-850S, and TS850 as the same product. The service manual PDFs that survive are largely encoded or binary, so no readable power output, frequency range, dimensions, weight, or original price can be pulled from them. What the repair community knows about this radio is more useful than the spec sheets would have been anyway.
The TS-850 isn't really a spec story. It's a design that worked beautifully until it didn't, and thousands of owners have spent decades keeping these rigs alive.
Key Features
The Four YM6631 DDS Chips on the CAR Board
The defining component of the TS-850 is a set of four YM6631 DDS (direct digital synthesis) chips mounted on the CAR board. Kenwood made these custom parts specifically for this radio, and they do a lot of work. They generate the RF frequencies used in the mixers, and they even produce the sidetone when sending CW. When they function, they're the heart of the radio's frequency generation. When they fail, and they do fail, they take the whole rig down with them.
The failure mode is well documented. Kenwood realized there was a problem and addressed it in the YM66312 revision of the chip. The new chips, as the repair community puts it, do not fail, which says something was wrong with the original design. There was no extended warranty covering the problem, and the new chips are no longer available to replace the old ones. Owners with the original YM6631s face the fact that it's only a matter of time before they self-destruct.
Serial numbers help identify at-risk units. If a serial number starts with the number "2," the radio may have the old DDS chips. Experienced repairers ask this first when someone reports weird behavior, then follow it with a check of which chips are installed.
Replacement CAR Boards and Modern Solutions
The aftermarket has stepped in where Kenwood's parts pipeline stopped. Someone finally designed a replacement CAR PC board using modern components, and these have appeared for sale on eBay. As of 2023, yet another replacement option for the whole CAR board became available through rfsystem.it. Original chips are essentially gone, so for owners who can't find them, these replacement boards are the way back to a working radio.
RF Board and Band-Pass Filter Quirks
The RF board sits underneath the radio, identifiable by its shiny shield. Some of the band-pass filters on this board are always enabled by the 74LS145 decoder chip, which is a useful detail when troubleshooting reception issues. Getting at the RF board means removing it entirely, which is a significant undertaking.
Static Protection and the Surge Absorber Modification
The receiver's 47K ohm DC input resistance is a known vulnerability. That high impedance can allow nearby lightning strikes to develop significant voltage at the input, and there's a theory that this contributes to chip failures. A common modification involves removing the surge absorber tube on the small PC board connected to the antenna connector, then tack-soldering a 1-2 milli-henry pi-wound choke across it. The recommended part is a Hammond 1535B, 2.2 mH. After the modification, the input presents just 2 ohms to ground DC, making it much harder for high static voltage to develop.
Optional DSP-100 and Display Notes
Kenwood offered the optional DSP-100 digital signal processor for the TS-850, and setup procedures for high-fidelity AM or wide-band sideband operation assume one is installed. On the display side, repairers have replaced the LCD ASSY to fix a garbled display. At least one bench report found the reference oscillator sitting approximately 70 Hz off frequency, which is a problem on a crowded band.
Historical Context
Kenwood produced the TS-850 from 1989 until around 1996, when the TS870 took its place in the lineup. During those years it became a popular transceiver, popular enough to inspire a dedicated repair page to help owners keep them on the air.
The parts situation is the central fact of TS-850 ownership. Getting new parts is almost impossible now, and most repairs require finding a donor radio to swap modules with. Kenwood's own position has frustrated the community: sympathetic people at the company have been unable to convince management to produce more of the DDS chips. The radio was well-liked when new and is now a test of owner resourcefulness.
Collectibility & Value
The TS-850 occupies an unusual place in the vintage market. People still want to keep them running, but because of the chip problem, condition and chip status matter a great deal. New YM6631 chips have sold for over $300 for a set of four, and complete CAR boards with four new chips have commanded similar prices. Pacific Parts sells some components online, but buyers should be prepared to pay top dollar, and Pacific Parts does not have the DDS chips available anymore.
Recent eBay listings have put working TS-850s in the $525 - $750 range. One Russian-market example, a TS-850S with power supply and manual, described as working at all 100 watts with excellent cosmetics, was listed at 55,000 rubles. A capacitor replacement kit with radial and SMD caps sells for around $50.
The most common failure points go well beyond the DDS chips. Owners report ALC voltage instability, with speculation that Kenwood may have installed capacitors backwards. The C1 capacitor on the CAR unit can leak. Carrier balance and carrier setpoint adjustments drift. Displays go dead. One distinctive symptom is a frequency display showing all dots while the radio sends "UL" in CW over the speaker, a sign of a PLL unlock condition. Low receiver sensitivity, no transmit audio on FM, radios stuck in send mode with no receive, raspy signals on some or all bands, and poor solder connections round out the list of known issues. Monitor function failures on SSB and CW, erratic passband tuning on SSB (though fine on CW), and noise blanker performance problems are also documented. Bench reports describe leaky caps and corrosion damage severe enough to require full recapping, and one owner noted a raspy sound in the audio that worsened as the radio heated up.
Some owners have given up entirely, parting out their TS-850s rather than chasing the chip problem. The sentiment in the repair community is raw: one longtime repairer states plainly that he will never buy a Kenwood radio again because of how the company handled this. Others express sadness that Kenwood isn't doing a better job standing behind their radios. For anyone considering a TS-850 today, the serial number and chip status are the first things to check. A radio with the old chips is a project waiting to happen, while one with the YM66312 revision or a modern replacement board is a usable classic. One reviewer who'd also run a Kenwood TS-440 and an Icom IC-703+ said neither came close to the 850's audio quality, transmitted or received, nor its selectivity. The internal antenna tuner has a wide range and has tuned even grossly out-of-resonance antennas.
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