Diagnosing an issue with C8PDF drive

[lowrybt1]

Thanks for your guidance.

I made sure J7 is seated as it should be. Then swapped in a spare TRK0 sensor from an identical Siemens drive, not knowing if that sensor might also be bad. Still saw the same symptoms. I ordered a replacement sensor (brand new) with IR LED and emitter/collector, to the best of my ability trying to line-up the voltage and current specs of the newly purchased sensor with the presumed failed sensor.

Wired the new sensor into the drive, taking care to match up LED and emitter/collector leads of the new sensor with the old wiring. Powered the drive PCB (not the drive motor) and loaded a floppy disk.) Voltages at TPA-2 and TPA-4 are unchanged. I tried various different pairings of the new/old sensor wires to see if that might be the issue but voltages didn't budge. It's possible that the new sensor simply is not compatible.

All the other (originally installed) sensor are working according to specifications. From the schematics, I see that the track zero circuitry also involves some resistors and a voltage comparator IC. I'm a bit out of my depth at this point. The good news: I have two working drives remaining.

Tom

[lowrybt1]

Looking again at the J7 connector, it seems there are a few slots (receptacles) where some of the contact/conducting metal has worn away. Do each of the slots (pin receptacles) on this connector have metal contacts on the top and bottom. I'll try to post a photo showing what I'm getting at.

[Thomas]

I do not know, how the connector should look like. I have somewhere two Siemens FDD 100-8, but not accessible at the moment.
If you have the sensor connected to J7 but not placed into the drive, you can check for function more easily. Placing something into the sensor to interrupt the light should have an effect on the TPA2 test point voltage. If TPA2 stays at 5V, use a flash light. If it still stays at 5V something with the sensor or its connector is wrong.

[lowrybt1]

You called it. I pulled another sensor (drive door closed sensor) known to be working and wired it in as the replacement for the bad trk00 sensor. I’m now seeing changing voltages on TPA2 and TPA4 that correspond to the blocking or unblocking of the trk00 LED. So, I’m going to put everything back together and test the drive. Things trending in the right direction.