i wouldn't expect to get good performance out of a cheaper used "as-is" fm3 w/o preparing to inwest some time &/or money into it...
If nothing is actually broken (like the unobtanium tuning cap or the power transformer) it should be a simple matter of replacing a few cheap tubes and doing the original alignment sequence *to the letter*. Essentially all parts aside from those are available including the eye tube as long as you don't mind paying for it. Frank was also correct, as usual, about which parts tend to go over the hill. The most important mod are the undersized resistors in the RF section - with the stock part these got so hot that replacing them noticably lowers the overall operating temperature of the of the entire unit and particularly the faceplate.
The Frank FM-3 modifications are simple, cheap, and well worth it, particularly the output coupling caps. The only problem I have ever had with an FM-3 was with the small "trimmer" caps on the tuning cap. Very fussy and very prone to becoming bent or flattened out and therefore unadjustable. When that happens you can get some very odd effects, like a sort of "mirror image" tuning where you can work you way up the dial and then all of a sudden notice that turning it more actually picks up stations at *lower* frequencies again. I just re-bent them and was able to restore the performance and adjustability.
Once you get it right the performance of the tuner part is about as good as anything else, including the selectivity (tested in the very difficult, crowded and RF-noisy Bay Area). And the sound quality is better than almost anything else.
I haven't tried any of the trick replacement parts from FM-3Zone, but the "selectivity filter" is intriguing.
The biggest problems I have had with "eBay" units is poor original construction and unbelievably filthy and smelly internals - not anything much broken. I usually take more time cleaning them out inside than I do aligning it. That's an appeal of the replacement circuit boards - it comes out with good solder joints and clean inside.
Brett
