I've always thought the Superscope Aircommand CB-640 was kindof a kewl radio. It was groundbreaking in its look and style for 1977, had some good features and claims of great performance. Or maybe I just fell for the Humphrey Bogart advertising. :-) Anyway, I wanted to have one working in my collection.
Over the years I bought 3 of them at hamfests, eBay, etc. None of them worked. They all had a similar failure mode. The receiver seemed sensitive, but wasn't receiving where it's supposed to be... and no transmit.
I found references on another discussion forum to cold solder joints on the PLL board. Anyway, I thought I would hunker down and fix one of them. The factory service manual is available on CBTricks, but since I find PLL circuits difficult to troubleshoot, I bought the Sams Photofact (#239) to supplement it. Between the two, I had an excellent picture.
First thing I found in all three radios, is that the PLL was out of lock
It turns out that the PLL circuit board is double sided. They used a number of rivets (I found 10) to interconnect the two sides of the board. These connections were failing. I removed the old solder with wick, and reflowed all 10 rivets. Back in business!
Of the 3 radios, 2 are now working well. The third radio did have failing connections at the rivets, but also has an additional fault, and will require more troubleshooting.
I'm posting this in the hopes that it can help someone else out down the road!