Motorola 63X2

I've been working on a Motorola 63X2. It's a vanilla AA6 that is part of a lot of AA5's and AA6's from an antique shop somewhere in upstate New York that I was given by a friend. They must have been the "tough dogs" from a service shop, because every one that I've put on the bench has had unusual problems. 


I tested and replaced the bad tubes  and then recapped it. 


I restuffed the multi-section electrolytic capacitor, but it was quite a struggle to get the guts out. The cardboard case is pretty marred. I used hot-melt glue to seal the ends. Not very pretty, but serviceable.


There were a couple of places that needed a type Y capacitor for safety (the blue disc caps).


I fired it up and heard some crackle in the speaker from the dirty volume control pot, so the audio section was more or less working. I checked the B+ and it was right on the money. Then I put another radio nearby and listened for a heterodyne from the local oscillator. Sure enough, I heard one, but the LO was aligned way high. I took a look at the oscillator coil (in the photo above), but it was fine.


I took another look at the chassis and realized the RF coil was missing its tuning slug (see above photo). I guess someone cracked the slug in the middle of aligning the receiver and then set it aside in the "dog" pile.

I'd like to find a replacement core for the RF coil, as it seems a shame to discard it after replacing it with a new one. The core is something less than 0.230" in diameter, perhaps around 0.225", and is externally-threaded.


Alan Douglas (RIP, OM) sent me a replacement core that fit perfectly. I've now got the radio aligned, but it seems somewhat deaf. My casual sensitivity test is receiving WFAT on 700 kc, a daytimer located in Orange, MA. Despite the RF stage, the 63X2 doesn't cut it. I'll have to try another RF tube and see if that helps. (My TV-2 is way out of calibration, so I don't trust its test results.) There's also lots of local RFI, so perhaps an isolation transformer or a couple of ferrite beads on the line cord might help.

© Steve Byan 2011-2019