justacruzr2 Posted May 15 Author Share Posted May 15 (edited) 2 hours ago, Stuart said: Step and Direction look OK. They will read opposite on the WD chip pins and on the floppy connector as there are inverters on the output of the FDC card. Does Step keeps pulsing even when the head has visibly reached track 00? See if you can work out how track 00 is detected - often by the head carriage operating a microswitch or breaking an LED sensor beam. Also see if you can follow the track 00 output on the edge connector back to a logic chip on the floppy drive circuit board - the 'mechanism' may be fine but a faulty logic chip on the floppy output. Track 00 is active low - so should be high until it reaches track 00 then go low. Have you got more than one drive you can test? Glad to hear that. This just got narrowed down to one thing. The track 0 sensor consists of 2 parts, the sensor itself which is "u" shaped and is located in a bracket at the end of the head travel. I believe it works like an "electric eye". The other part is a finger extending from the side of the head carriage. I think what happens is that when the head position reaches the end of its' travel to the outer edge, the finger breaks the LED sensor beam and should then set the track 0 register to LO. According to the datasheet, if this input is not received it sets a seek error. And that sounds very much like what's happening. OK, I'll have to follow the circuit traces downstream to see what other devices (ICs, caps, resistors, transistors, diodes, etc) are involved. The STEP test stopped pulsing when it reached track 0. And yes I do have another drive. 2 more in fact. One of the 2 is the brother of the drive I'm currently testing. It was in the PEB at the same time as the spike so probably has the same problem. I will do those tests again on it if you think I should. PS Love using that logic probe. Should have got one years ago. Edited May 15 by justacruzr2 more info Quote Link to comment Share on other sites More sharing options...
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