[Collins] Help on troubleshoodint a 51S-1

[Bill]

A TUF mixer will have 50 ohm impedance levels on all the ports. Don't
know what
 the tube system is setup for.  I suspect that if you used the (forgive
my spelling here)
 Schottky diodes (0.2 V forward voltage) you would get good mixer
action.  

 As I recall the SSB selection is done by filters center high or low
about the LO
 port of the mixer. Possible that the filters or LO are off.  Should be
able to 
 check the pass band tuning by tuning in a cw note.

 If the LO is noisy, it will be imparted onto the audio.
 

 I have my own recapping job to do on one of mine :).


Good luck

-----Original Message-----
From: collins-bounces at mailman.qth.net
[mailto:collins-bounces at mailman.qth.net] On Behalf Of DW Holtman
Sent: Wednesday, September 12, 2007 8:05 PM
To: collins at mailman.qth.net
Subject: [Collins] Help on troubleshoodint a 51S-1


Hello,

I recently acquired a 51S-1. I spent a good deal of  time cleaning the
complete receiver and treating the contacts, switches etc. I have a
problem now that I was wondering if anyone had seen before. 

AM works great. USB and LSB have a lot of distortion. Signals on the air
can be heard, but it is raspy and very difficult to understand. Looking
at the schematic, there is only the Product Detector and SSB/CW Pre-Amp
that takes a different path from the AM signal. 

I ordered the C162 and some 1N34A diodes. Has anyone had problems with
old Germanium Diodes breaking down? The Cap could have dried up. I
ordered all of the electrolytic caps in the receiver from Digi-Key.

What are the thoughts on replacing the old rectifier diodes with
something newer? This is the first receiver that I have worked on for a
couple of years with a solid state product detector. I'm not going to
modify it, but I bet a product detector/mixer from Mini Circuits in the
TUF-1 family would improve the performance. 

Any suggestions or ideas on similar problems with this receiver would be
greatly appreciated. Also any suggestions on alignment. I have looked at
the manual and it is long and involved.

Best,
DW Holtman
WB7SSN ______________________________________________________________
Collins mailing list
Home: http://mailman.qth.net/mailman/listinfo/collins
Help: http://mailman.qth.net/mmfaq.html
Post: mailto:Collins at mailman.qth.net