Second tuner also now works. I had to replace the RF modules in both of them -- one got a factory original pinched from an NFG tuner I got from Hugo's junk pile (thanks Hugo!), the other got one of the PCATS modules, with appropriate modifications as described in an older thread.

The two old failing modules were removed using hot air, and could perhaps be repaired someday. Rumour has it that an op-amp chip inside the module is the problem. So I'll file those in case I someday need them, and then try to identify/find/replace the op-amps.

Cheers