Original IBM PC (was Re: Prices to pay for old

[IBM PC floppy drives] I've got the Type 1 drive schematics here (from the O&A TechRef volume 1). Let's go through the obvious things first. You have a DIP shunt (a little plastic block with shorting bars) in socket 1E of both drives, right? And a termination resistor pack in socket 2F of the drive physically furthest from the controller. Check that the cables on J4 at the back of the logic board are connected properly. There are some blank pins (4?) nearest to the edge connector, and then P8-P12 in order along the pins. Also, check the supply voltages - +5V and +12V at the drive when the machine is turned on. You do have the power cables plugged in, I trust :-) (don't laugh - I've forgotten them). OK, let's sort out the lack of LED first. Unplug the cable from the controller (leave it hooked up to the drives) and turn on the machine. Ground pin 3 of IC 3E (a 7407) in the drive. Does the LED come on now? If so, then suspect the controller, DIP shunt or cable. If not, then ground pin 4 of IC3E. If the LED now comes on, then IC3E is defective (or not geting power). Problem is, if IC3E is defective, then how many other parts have been damaged. 7407's are pretty reliable, so if it's damaged, it sounds like power problems. You didn't hook up the power cable backwards, did you? You can trace the motor on signal similarly. Try grounding pin 16 on the edge connector (the even numbered pins are on the top of the board, starting from the end nearest to the notch in the connector tongue), or equivalently pin 1 of IC3E. If the motor doesn't start,then try grounding TP13. If that starts the motor, IC3E is defective. If the motor still doesn't start then I'll have to talk you through the motor control board at the back. -tony