[Collins] Help on troubleshoodint a 51S-1

[DW Holtman]

Hello,

Thanks to everyone who had suggestions, I basically tried all of them. Where

 After lots more troubleshooting, I found that the BFO was FMing. It looked
like a classic 5 or 10 KHZ FM signal. I replaced C162 (along with every
other lytic in the receiver) in the base of Q1 (SSB/CW Pre Amp) and the
FMing stopped. It showed good stability on a frequency counter (it was
bouncing around a couple of KHZ before) and visually on a scope. But, the
raspy signal on SSB/CW is still present. I injected an audio signal on the
base of Q1 and it produced clear audio. That pretty much takes me back to
the balanced bridge diode mixer/product detector. All of the diodes read
around 0.3 volts using the diode range on my Fluke meter, might have to
change out the diodes. Is there anything better than 40 year old 1n34A's  to
replace them with?

Any other suggestions on options besides changing out CR1,2,3 and 4? AM has
nice clean audio.

Best,
DW Holtman
WB7SSN