Floppy drive track-0 issues

It may not be the head, but it shouldn't he hard to check... Firstly, clean the heads -- not with a cleaning disk (no matter what the manuals may say), but with a cotton bud and propan-2-ol. I once spent an afternoon chasing a non-existant fault on the analogue board of a CBM 2850LP that turned out to be drity heads. Secondly, most dosk heads have 4 connections -- if there are actually 5 wires on the connector, then the last is most likely a screen (do any of the pins on the drive pCB connector test as grounds? If so, it's almost certainly a screen). The 4 connections are the 3 wires of a centre-tapped reand/write winding and one end of the tunnel erase head, the other side of that goes ot the centre tap. Just occasionally you come acrooss other arrangements. One is to have the erase head totally flating wrt the read-write head, so 5 wires. Another is to include some or all of the switching diodes in the head assembly. Look for SOT23 pacakges on the flexiprint to the heads. Sony once made a double-sided head assembly with 6 wires and with the all the switching diodes on the flexiprint, but they went away from tlat on more modern drives. You cna test the head windings for continmuity quite easily. If you're worried you may have magnetised the head by so doing, you can demagnetise it using a tape head demagnetiser. The head windings are low-resistance and will essentially show as a short-circuit between all 4 head connections. If the head checks out, trace form the head connector on the PCB to switching diodes, often doube diode units in SOT23 packages. Check them, replace if necessary. The centre tap pin most likely foes to a transistor, part of the head swtiching circuit, I've had that fail before now. Again, easy to check and replace. That Sony model number sounds somewhat familiar to me. Is it a normal-size (half-height, techniclly 3.5" unit with a logic board iwth 2 large PQFPs on it (one for the analouge circuitry and one for the digital circuitry)? And a positiion at the rear right corner of the main chassis that could be used to mount an eject motor unit, like a Mac drive? If so, grab the HP9114B (must be B) diagrams from http://www.hpmuseum.net, IIRC that uses a similar drive. Those 2 seem inconsistent. The first says that TRK00 is never asserted, the latter gices a time when it is. Which is it? I've seen floppy drives that do odd things if, for example, one of the input signals is asserted on power-up. But never this. I assume the control logic is one ASIC :-(, so you can't investigate it. What signals are you asserting when you try the seek? You don't have write-gate asserted or anything silly, do you? Silly suggestion. Connect it to your PC and do some seeks. Use a logic analyser to see what the signals to the drive are doing. Then see how the signals from your excersiser differ. Yes, that sounds right. -tony