[Kenwood] TS-940S Low Volume Problem Solved

[Edward McCann]

Hello all:

As Paul Harvey would have said, and now for the rest of the story.

I addressed many of the valuable suggestions from those who took the time to respond, for which I thank you. Nothing seemed to work. 

I addressed some of the suggestions from the TS-940 lore, beginning with the "check all gray/coax leads. Didn't count them but it was a big number. Used tiny bit of De-Oxit at each one touched, moving methodically along. But no increase in volume, no intermittents appeared.

It wasn't until I used my wooden chop stick to gently nudge the cable harness running from front to back of the rig just above the control board. It moved, and a blast of audio came from the speaker. When I removed chopstick volume went back to low.

Lacking resolution from the service manual downloaded from the web, I took several iPhone pictures of the control board (to be able to reassemble the connectors.) Armed with the photos and page 94 PC Board View of the Control Unit and the Terminal Function pages 87 and 88 it finally dawned on me that the harness was held together so tightly, moving in the main section moved bits and pieces down the line, in the vicinity of connectors 36 (audio signal for external speaker, among other things, which I had previously ruled out since the headphone jack had the same low volume), 37 (AF Gain VR, which if I had been clearly thinking I would have stared with, instead of cleaning the gray coax connections throughout the radio) and 38. 

I couldn't quite replicate or trigger the intermittent by nudging each of the three connectors, but I did disconnect them, and used the De-Oxit at all three. After reassembly of these three connectors, volume was back to an appropriate level.

Moral of the story: I should have headed first to these connectors. Pretty dumb when you think about it. After all, they all were in the AF loop.

Summary: the chopstick moved the harness, and one of the many harnessed wires downstream moved (without being noticed).
I nudged it gently more than once, but one of the moves wiggled the connector just enough to trigger the intermittent. I don't know which connector was the problem, since I lost the scientific method at the end, eager to solve the issue.

Lesson Learned: the iPhone took some great detailed photos, with great resolution and the ability to blow up without distortions, all of which were extremely helpful in reassembly without tears. 

I have a much better set of coax connections I guess, so maybe I have forestalled some other intermittent, at least for now.

Again, thanks to all of you for great suggestions.

73
Ed McCann
AG6CX


Sent from my iPhone