Kenwood TS-940 / TS-940S

A 100-watt HF transceiver that owners still call one of the best radios Kenwood ever built. A dirty connector will give you trouble long before a pileup does.

Overview

The TS-940 is a Kenwood HF amateur transceiver, an all-mode rig covering the amateur bands from 160 through 10 meters. Sources use the names TS-940, TS-940S, and TS-940SAT more or less interchangeably, and no source in the record draws a clear line between them. Treat them as the same radio with different badges. One Russian classified listing dates the model to 1986 and calls it a Hi-End model of the Kenwood corporation. That is the only year reference in the available material, so anything tighter on the production run is guesswork.

On paper the radio is a 100-watt output transceiver. Owners consistently describe it as sensitive, with a transmitter that punches above its rating. One owner bought his new in the late '80s and came back to the model decades later. He wrote that the rig still sounds as good as he remembered. The radio earned a reputation as a classic, and it also comes with a very specific set of maintenance problems, covered below.

The available documentation does not give the TS-940 clean, well-understood service literature. The service manual's circuit descriptions have confused and frustrated owners and technicians for years, and there are documented errata in the design descriptions. That causes trouble, because a radio this well-loved attracts a lot of modification advice, and a lot of it gets applied by people working from a manual that doesn't quite match the radio.

Key Features

100 Watts, and More Than That in CW

The headline number is 100 watts of output power, which is the standard ceiling for an HF transceiver of this class. In practice, owners report the TS-940S will put out 150 watts or more in CW mode. The documented advice is to hold CW output to no more than 110 watts. The reasoning is blunt: the extra 1.4 dB, which amounts to about a needle width on your contact's S-meter, is not worth the risk of damaging the final transistors. If you plan to run CW hard, take that caution seriously.

Automatic Antenna Tuner

The TS-940SAT variant includes a built-in automatic antenna tuner. That is a real convenience on a radio that covers 160 through 10 meters, since a single antenna rarely loads cleanly across that span. The sources tie the tuner specifically to the SAT designation. The base TS-940 and TS-940S are not explicitly described as having it, so confirm before assuming a given unit includes one.

PIN Diode Front End

The radio uses PIN diodes, and Kenwood's own promotional brochure for the model includes a section on how PIN diodes were discovered to improve radio performance. Owners also commonly replace PIN diodes with modern equivalents as part of a refresh. As covered below, the more experienced voices in the owner community argue that this should not be the first thing you touch.

PLL and VCO Design

The TS-940 uses a PLL-based synthesizer, and there is a documented failure mode: PLL unlock on the lower frequencies, attributed to low VCO levels. Kenwood's own service documentation for the symptom describes a change that increases the VCO level and should prevent it from recurring. If a TS-940 refuses to lock on the low bands, look there first.

DC-DC Converter and Power Supply

Internally the radio contains a DC-DC converter with electrolytic capacitors, a power supply block, and an AVR board. The electrolytics in the DC-DC converter and in the rectifiers are a known wear point, and replacing them is a documented repair for weakened reception. Separately, the power supply and PA sections of Kenwood and Icom transceivers purchased between roughly 1993 and 1997 were built with a pair of bad electrolytic capacitor batches. That is a broader industry problem and not unique to this model, but it matters if you are dating a unit.

Connectors with Silver-Plated Contacts

The radio is full of multi-pin connectors with silver-plated contacts. This sounds like a build-quality footnote. It is actually the single most important thing to know about owning a TS-940, and it gets its own section below.

Modes

Sources describe the radio as all-mode and mention LSB, USB, AM, and CW in actual use. The manufacturer's documentation confirms the radio supports SSB, CW, AM, FSK, and FM modes.

Historical Context

The TS-940 dates to the mid-1980s. One listing identifies it as a 1986 Hi-End model, and it is remembered as a classic HF transceiver and one of the best radios Kenwood made. A new unit sold in Sweden in 1989 for SEK 26,250. It is mentioned alongside the Kenwood TS-930S in the parts and classified community, though no source in the record states an explicit family hierarchy between the two beyond the shared TS-9xx naming.

One detail for anyone considering an aftermarket upgrade: the TS-940 upgrade kits went through five different revisions before release. Getting this radio right took iteration, and that is worth remembering when reading the modification literature around the model.

Collectibility & Value

No current market prices were found in the research, so this page does not guess what a TS-940 sells for. The record does give a very clear picture of what goes wrong.

The dominant fault, by a wide margin, is poor contacts in the connectors. An experienced owner puts it at 80% of all faults in the 940. The recommended fix is mechanical and unglamorous. Inspect and clean every connector. Pull the pins and clean them with a brush and alcohol, and work the female sockets with a toothpick and alcohol. Then treat the silver-plated contacts with an aerosol contact cleaner (Kontakt 60 is the one named), and follow that with alcohol again, because the reaction products of silver oxides remain on the contacts afterward. The second most common cause is poor soldering on the connector pins, cured by re-soldering them.

The third cause is more serious: local oscillator frequency drift or outright failure, caused by aging of the ferrite cores in the oscillator coils. The warning is emphatic. Do not attempt blind adjustment, because some of the coils have very sharp resonance and you will make it worse. You need a frequency counter and a tube voltmeter or oscilloscope to do it properly.

The documented modifications include a synthesizer mod with a pair of op-amps, power supply and AVR board changes, PIN diode replacement with modern parts, an LCD clock display fix, a talk power improvement, an erratic display fix, and an ALC mod. There are also aftermarket supply upgrade boards and documented FET swaps with field measurements of receiver improvement. The community advice on sequencing is sensible: get the service manual, restore the transceiver to factory state first, do the power supply and AVR work, and only then consider the synthesizer and PIN diode changes. At least one long-term owner is blunter: forget the mods, don't break the unit further.

On the parts side, displays for the TS-940S circulate in the used market, and amp cables with DIN mounts are listed for the model. Corrosion on the PA boards is a reported condition on at least one example and is described as fixable. A dead backlamp on the slope display is the kind of minor cosmetic fault that shows up in listings. The general buying advice from the owner community is direct: check what you are buying, because there are bad ones out there.