[Milsurplus] AN/GRR-5 Questions

[Richard Brunner]

Wayne Hertel wrote:
> I am expecting delivery of two AN/GRR-5 Receivers shortly - winter 
> project. I have a copy of TM 11-295 dated August 1952.
..... Anything unusual I should be aware of, other than the usual leaky
> electrolytic capacitors?

Yes.  Study the schematic - there are two vibrators, one for B+, and one 
for the filament supply.  The vibrator driver coils work directly on 6 
volts, and through dropping resistors on 12 and 24 volts.  The 
originally specified vibrators work fine, but non-original replacements 
may not.  The one I worked on had a replacement for the filament supply, 
and it didn't want to work well with dropping resistors, and reducing 
the dropping resistance to make it work harder wasn't satisfactory 
either. I ended replacing it with a transistor flip-flop, which worked 
fine.  There is a about 20 point relay which changes from dc to ac 
input, and I had to bend about half the leaves to make proper contact. 
Plan on replacing the selenium and copper oxide rectifiers with silicon 
- it's satisfactory to merely bridge across them, and don't forget to 
add some additional resistance to accomodate the lower forward 
resistance of the silicon rectifiers.  In the end you will have pretty 
nice receivers.

Richard Brunner, AA1P