Hi Group: I realize there aren't too many TR-6 users out there, but I hope that someone on the list may have encountered these problems with their TR-4 series rig, and the solution hopefully will be the same for the TR-6.
The problem first began with the transmitter "hanging up" for 1/2 second or so on transmit, before going back to receive. The bias was also abnormally high, like 250 mils, or so. At the same time, I noticed that the output would drop, sometimes to nothing while this was happening. In other words, while the "hangup" was occuring, speaking into the microphone did not result in any output or variation in output. Then, for no apparent reason, things worked fine again, for awhile. It also appeared to be heat related, in that the rig would work fine when cold, and then the problem would develop again after warmup. The problem became worse, and more frequent as time passed. I suspected that the bias circuit had gone bad, and was going to install the upgrade board in the the AC-4 anyway, so did that, and all voltages, including the bias at -60 volts, appear nominal after the new board was completed and installed in the AC-4. I also changed out the 6EV7 vox tube, as I suspected it might have something to do with the "hangup" part of the problem. Now, I cannot set the TR-6 bias below 200 mils during the bias setting procedure. The "S" meter goes way up to 60 over S-9 during the bias setting procedure. The "hangup" problem is still present, too. Receive appears normal in all respects. I have measured the bias voltage at the feed-through cap going to the grids of the three output tubes, and it reads -60 volts both during receive and during transmit. I have changed out all of the three output tubes with substitute tubes at least checked to be operational, with no difference in the bias setting problem. Any ideas or suggestions? Thanks very much es 73, Mike K6NC
