[Collins] Help on troubleshoodint a 51S-1

[DW Holtman]

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