Turner Plus Three initial spike

[Dmitry_ONx]

Hello Team,
I was troubleshooting low drive of Turner Plus Three when used with Drake TR-4. The issue was that I had to dial mic preamp and rx gain on the radio to the maximum to get reasonable RF output on the wattmeter. The transceiver was working just fine with Shure 444, so the issue was definitely the Turner mic. I replaced all electrolytic and tantalum caps on the PCB board and it seems to have solved the drive issue. One problem remains however: the RF output is low for about 2 seconds at the start of the transmission and then it comes up with to where it should be (seen on RF wattmeter). I measured audio output of the Turner with the oscilloscope, and I see very brief spike at the beginning of the transmission. Duration is less than a second. It then stabilizes and stays stable. I release the PTT and then start the transmission again, the behaviour is the same. I am thinking this initial spike forces AGC of the transceiver to overload. I use fresh lithium 9v battery. Electronic components are only on the PCB board although I saw pictures on the internet with a small cap across the PTT switch. Any ideas of what I can further check is welcome!

Thanks a lot in advance!
Dmitry ON2DE

 

[nomadradio]

It sounds like a timing issue. The lever contacts should close the battery power before closing the audio-output circuit. A prior attempt to "adjust" the contacts by bending them can create this issue. Really sounds as if the audio output circuit is being closed before the battery circuit.

73

 

[Greg T]

It sounds like a timing issue. The lever contacts should close the battery power before closing the audio-output circuit. A prior attempt to "adjust" the contacts by bending them can create this issue. Really sounds as if the audio output circuit is being closed before the battery circuit.

73

That was exactly my thought as well, since I just had that exact same issue. One of my +3s would give a crunch on key-up and it took me a while, but did find the issue. Instead of bending the reeds, I used a shim, very thin card stock to tighten the gap a bit. worked perfectly.