[Collins] Help on troubleshoodint a 51S-1

[Bill]

Try hot carrier diodes or schottky diodes. Voltage drop is about 0.2
voltages and 
switch on much harder than germanium. Makes for better switching hence
mixing

-----Original Message-----
From: collins-bounces at mailman.qth.net
[mailto:collins-bounces at mailman.qth.net] On Behalf Of DW Holtman
Sent: Monday, September 17, 2007 1:29 PM
To: DW Holtman; collins at mailman.qth.net
Subject: Re: [Collins] Help on troubleshoodint a 51S-1


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


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