TEC FD-50x drives - known issues?

One of the problems with this list is that it's impossible to know the knowledge/skill level of the person asking the question. Your original question did seem to suggest you thoguth of the floppy drive as a single unit, whereas as we both know, it's a collection of several systems. It certainly helps if we both know which of those systems is the problem. Ah, right (or is that Ah... Write :-)). Can you identify the read amplifier chain (often using NE592 ICs), or is it hidden in an ASIC. In the latter case, look for a pair of LC filter networks connected to the ASIC. The read chain almost always consists of differential amplifiers right up to the final comparator stage, so you expect filters to come in pairs, etc. If you can find a pair of test point pins associated with those, then they're almost certainly the outputs you'd use for head alignemt. Hook a 'scope with differential inputs to those, try reading a normal disk (never put an alignment disk into a dodgy drive!). Do the signals look at all sane? I don't know how complicated these drives are, but I can't believe it would tkae more than a day to figure out the read amplifier section, even if it is hidden in the ASIC. Sometimes it's quicker to just sit down and have a go :-) Well, I like to keep my machines as close to original as possible. -tony