Kenwood TS-940S

Yes, I bought a TS-940 and have been trying to diagnose hilarity.

Marker

The calibration marker circuit is .. sub-optimal, and picks up a lot of stray, random noise throughout the radio.

There’s a very nice write-up about this, applicable to at least the TS-930 and TS-940:

Power supply issues

The TS-940 power supply is not the best designed and it’ll go pop, taking your hard-to-find driver transistors with it. (k6iok)[https://k6iok.com/] has replacement power supply bits to drop in and it works!

My issues!

K6IOK installed his replacement PSU in my TS-940 and it runs like a charm! The radio runs much cooler and it’s much lighter. However, I’ve been having some RF issues which I bet are due to this rig.

PLL repair / recalibration

“Melt the wax out of VCO-0 (the one next to IC19). This is to allow easier resoldering of the components. Turn the board over and remove the old solder and resolder all of the parts that are inside the enclosure. Pay close attention to the leads on L35. Clean any potting compound on the bottom of the board especially under the cap tacked on the bottom of the board. Once clean and resoldered install in radio and adjust the coil for 7.5v at the TP. If stable and operating then you may repot if desired but not necessary.”

For reference: https://forums.qrz.com/index.php?threads/ts-940s.448583/

Dry / Wrong Electrolytic Capacitors

This radio runs hot. Very hot. I found two fun issues here:

There are around 190 electrolytic capacitors to replace in this radio and it’s worthwhile doing it.

PDFs