RCA AR77/GR10 Communications Receiver

[Gerry O'Hara]

Just finished work on an RCA GR10 (RCAF version of the AR77). The work comprised a good cleaning, re-capping (using mainly using NOS Aerovox caps - all pre-tested ok), replacing a couple of resistors that had drifted significantly out of tolerance, cleaning the switches with De-oxit, installing a line fuse, etc. It is now burbling away happily on WWV at 5MHz on a bit of wire in the basement on soak test before I check alignment fully (it is not too bad - <100kHz out on 5MHz WWV). I have not fully tried it out on all bands, but it is better than I thought it would be considering its relatively simple circuit. The twin shutter dials (main tuning and bandspread) were a bit fiddly to get working correctly - they were gummed-up with hardened grease and dirt, plus, if you look at the vertical mounting plates on the photos below, plastic residue from the dial ‘glass’ (Plexiglas). Once working, I noticed it was a bit 'deaf'. This was traced to the first IF stage - it was a strange fault that took a little time to resolve: zero volts on the screen grid and the S-Meter not working. After a frustrating hour or so checking associated resistors and capacitors and the tube, the problem was evetually traced to a small sliver of metal that was shorting the tube socket pin to ground (very frustrating as it was almost invisible). Once it was removed, the S-Meter functioned correctly and the gain came up to what I would expect. Overall, the set is not in too bad a shape – I decided to leave the old, yellowed Plexiglas dial glass in place as it adds real ‘character’ to the dial, vernier and S-Meter (check out the photos) - you get that lovely cosy feeling in a darkened room while tuning around the bands. The crystal filter works a treat and CW performance is pretty good, but it is best on AM – really good audio quality. Final tune-up and a little cosmetic touch-up on the front panel and I am done.

Click on the photos for a larger image.

Gerry, VE7GUH