Kenwood TS-950

A flagship HF transceiver line known for its audio quality and a sub-receiver that can sit on a different band. The output stage has kept repair benches busy for decades.

Overview

The TS-950 name covers a family of Kenwood HF transceivers, not a single box. Sources reference the TS-950S, the TS-950SD, and the TS-950SDX. Kenwood's own documentation groups them together, describing "the TS-950SD, TS-950SDX and TS-950S radio transceivers" as offering "a variety of features for amateur radio operators." A documentation index lists the group as the "Kenwood TS-950 series," running 24 pages. The available material doesn't spell out how the base TS-950 relates to its suffixed siblings. Treat the variants as distinct models when shopping for parts.

The line is remembered for receiver flexibility. On the TS-950SDX and the TS-950 generally, the sub-receiver can be tuned to a different band than the main receiver. Three separate sources confirm this for the SDX, and it is documented for the TS-950 as well. On a crowded band, that means listening to 20 meters while watching 40, or working a split pileup without giving up your running frequency. It is the most consistently documented feature of the family.

Owner sentiment, where it survives in the record, runs warm. A seller listing a TS-950SDX described "incredible audio transmit and receive," and a YouTube presentation on the same model calls it "the best HF transceiver Kenwood ever made." That is enthusiast language, not measurement. No independent lab review of the TS-950 family appears in the available documentation, and no bench numbers for sensitivity, THD, or S/N were found.

One variant, listed as the "KENWOOD TS 950 SOX," carries a stated output power of 150 W. Nothing in the sources confirms whether "SOX" is a typo for "SDX," so attach that power figure only to the listing it came from, not to the family as a whole. No output power specification was found for the base TS-950, TS-950S, TS-950SD, or TS-950SDX. The TS-950S is documented with a frequency range of 10-160 m plus WARC bands.

Key Features

Sub-Receiver on a Separate Band

The headline capability of the TS-950SDX, and per the modification literature of the TS-950 as well, is that the sub-receiver can operate on a different band than the main receiver. It isn't a dual-watch gimmick. An operator can monitor a second band while holding a frequency on the first. The feature is corroborated across the SDX documentation and appears in Kenwood modification notes for the base TS-950, which suggests it was designed into the line and not bolted on to one variant.

TS-950SD Speech Processor

Kenwood's documentation for the TS-950SD references a speech processor, with a corresponding note about speech processor noise. The speech processor was the standard tool for squeezing intelligibility out of a crowded band. Its presence on the SD marks it as the more fully equipped of the two main transceiver versions documented. No processing specifications or measured performance figures were found.

Memory Write Protection via a Single Cut

A documented modification for the TS-950 lets the owner write-protect all memory channels by cutting a single trace - D18 on the Control Unit. It is a hardware fix for a software problem. It shows up in the modification literature because owners wanted it and the factory did not provide a switch. The same modification archive documents a general coverage transmit mod for the TS-950SD and a "Power On Functions" modification, both of which appear in more than one source.

Output Stage: MRF429MP and 2SC3133

The TS-950SD's final stage uses MRF429MP output transistors, the "MP" suffix denoting a matched pair, driven by 2SC3133 transistors of Motorola manufacture. The TS-950S originally used MRF429 devices in the output stage, with the circuit later modified for MRF 151. These are the parts that define both the rig's capability and its reputation on the repair bench, and an experienced buyer asks about them first.

Carbon Bias Resistors — the Known Weak Point

The carbon bias resistors feeding the MRF429s are documented as a recurring failure. They burn out, and the damage is not visually obvious, so a transistor can be destroyed before anyone notices the resistor has failed. The recommended replacement is a non-inductive part. This is the most useful piece of maintenance knowledge in the record for this radio, and it applies specifically to the MRF429-equipped variants.

Historical Context

The available documentation does not establish production years for any TS-950 variant, and no original list price was found. One seller, listing a TS-950SDX, stated that "this radio is 32 years old" - an owner's estimate, not a manufacturer date. Kenwood's own documentation groups the TS-950SD, TS-950SDX, and TS-950S together as a series, and at least one seller described the SDX as the "Flagship Kenwood TS 950SDX." A modification and repair document archive lists "TS-940 PA drivers replacement" alongside the TS-950 documents. No source in the record establishes a lineage or shared design between the two model lines, so don't assume a relationship.

Collectibility & Value

Asking prices vary widely and no confirmed sold prices were found. A TS-950SDX listed in Wexford carried an asking price of €1,000. A Russian-language forum listing for a TS-950 SDX described the unit as in excellent condition with a 220 V power supply and fully functional, at a stated price of 1800. The source doesn't give currency or units, so don't read it as dollars or euros. A TS-950SD appeared in a UK dealer listing sold as seen with no warranty, which is the realistic condition most of these radios now surface in.

The repair record gives unusually specific buying advice. Output transistors and drivers are the known failure points, and the carbon bias resistors that feed them can fail invisibly. Owners report successful substitutions. 2SC1969 goes in place of the 2SC3133, which works normally but needs mica insulation from the case and has a different pinout. With modification, a domestic КТ980 replaces the MRF429MP. An MRF-428 matched pair is reported to work excellently in the output stage with no reduction in output power noted across all bands, and at significantly lower cost. MRF transistors can be ordered from Chinese suppliers at prices reported between $27 and $70 depending on source. The 2SC3133 is reported available from CHIP-DIP at roughly 100 rubles, with one owner reporting a purchase at 50 rubles. A stabilizer transistor is cited at about 100 rubles.

Documented operational complaints include low power output after thermal protection engages, infinite SWR at the beginning of a transmission, smoke from the antenna tuner unit, a transmit spur on the TS-950S and SDX, and a click noise when the notch filter is engaged on the SDX. Test for these before money changes hands. Repair and modification documentation exists for the general coverage transmit mod, the power-on functions, and the sub-receiver band independence, and a Japanese-language repair writeup for the TS-950SD is referenced in the owner community. Spare parts do surface: a coil listed under the TS-950SDX part number, and an IF unit board described as fitting the TS-950S or SD.