I had a near Derb-like radio frustration experience the past weekend.
My relay system has had an annoying flaky T/R relay problem for the past several months, but I have tolerated it, since I can usually fix it whenever it acts up by clicking the T/R switch several times with the main rig switched to standby.
I decided to re-route some of my 500-ohm audio lines this weekend. I use a patch panel, and when I run the minidisc player to the transmitter, I have had to flip a couple of switches and plug in a patch cord,
always forgetting to turn the monitor off when going back to the live mic, resulting in an ear-splitting acoustical feedback squeal. So I re-routed some of the lines and added a 4PDT switch that allows me to flip a single switch to go from live mic to recorder, and automatically activate the T/R function of the CQbot.
When I got the new switch installed and everything rewired, the first time I tried it out, the audio level was there, but down about 40dB. Checked everything out, no wiring errors, no shorts, no loose wires, and the switch contacts checked out OK. I cleaned the male patch cord, thinking there might be corrosion, since I don't change the patches around very often. That seemed to fix the problem.
The very first time I tried the new setup, the old T/R relay problem got to be really annoying, with the transmitter dropping out in the middle of transmissions, or not going into transmit at all, so I decided it was time to bite the bullet and try to fix the problem once and for all. I pulled out the relay control unit and the little perf-board relay board, and examined the wiring. Nothing loose, but I noticed that I could wiggle one of the relays and another relay in the circuit would go spastic. While probing the wiring with the DVM, I accidentally shorted something out, sparks flew, and the trouble cleared up. But I put the whole thing down to eat dinner, and when I returned, it was acting spastic again. Never could find anything obviously wrong with the relay or its associated wiring, so I decided to replace the relay, since I have a supply of spares on hand, and hope that might cure the problem. After I rewired the new relay back into the circuit,
it too caused one of the other relays to go spastic whenever I wiggled it. But then I realised it was causing a different one of the other relays to drop in and out when the same one was wiggled. Then as before, I accidentally shorted something out, sparks flew, and the trouble cleared up once again. But this time, I never could make it flake out again, so I put the thing back together, and so far, no more malfunction. But it frustrates me that I never was able to definitively find the cause of the original problem and I still don't know whether or not it is fixed, since the original problem would occur, then it might work perfectly for weeks before it occurred again.
When I got it all back together, I decided to try the transmitter on the air to make sure everything was OK. The audio problem was back! Microphone output was 40 dB down once again. So I started probing around with an audio level meter to see if I could find where I was losing signal. A meter probe slipped, and bingo! The audio was normal once again! I was tempted to take a sledge hammer to the whole thing by then.
I took a cotton swab and cleaned the interior of all the patch panel receptacles with some WD-40, and the swab came out covered with black crud, so maybe it was oxidation of one of the receptacles in the patch panel that was killing the audio, but I won't know until some time has passed and the problem hasn't re-occurred.
And I still have an infrequently recurrence of severe audio distortion that cures itself when I turn up the gain and shout into the mic, but never sustains itself long enough for me to track down which stage is causing the problem. That first happened several years ago, but it hasn't happened for a couple of months now. That,too, may remain in hiding for months at a time before recurring at the most inopportune time. All I know is that it occurs somewhere between the speech amp and the main audio line that goes to the selected transmitter.
This is very typical of my radio malfunctions. Very rarely do I ever have a simple, straight-forward textbook failure. 99% of the time, it is something bizarre, off-the-wall that you would never expect in a million years, and
intermittent!
