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Disk II drive not spinning up

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My Apple II Plus goes straight to the basic prompt instead of spinning up the Disk II drive in wait of a floppy. The drive is just quiet and does nothing. I got it working for a short period of time, but then it died again. It has power though. Where should I start my troubleshooting?



Long version


I just picked up my first Apple II (Plus) the other day and now I'm going thru everything, step by step. The first problem I had to tackle were some keyboard issues. But after re-soldering and changing a few switches all keys worked.


My next problem was the Disk II drive. It didn't start at all when I tried it the first time. I took it apart, inspected all components, cleaned it a bit and re-attached all connectors. After which it came to life. I could load a few programs from floppy and all seemed good. Then the keyboard started to behave weird again, typing wrong characters and after some time no characters at all... I decided to put the computer away for the day.


The following day I managed to fix the keyboard problem by re-seating and cleaning the chip at position A3. After a few reboots everything was normal again. Time to try some more floppies. And now the Disk II was dead again...


So what happens when I turn on the computer is it goes straight to the basic prompt. It does not wait for the drive. The drive does not spin and the head doesn't re-calibrate. I've measured the voltages on the drive connector and they seem ok. I can see the drive LED flash slghtly when the computer is turned on and when turned off.


Where should I start troubleshooting? Can it be the controller card? I've tried it in both slot 3 and 6. If I try the "PR#6" command the cursor disappear and then nothing more happens.


I should also add that I downloaded a diagnostic disk and converted it to audio (using the c2t tool) and after loading for 10-15 seconds it goes to some "INSTA-DISK" screen, the disk drive spins up for a few seconds (while making some noise, not the normal head calibration noise), then gives a "DISK ERROR". So it shows the computer has some control over the drive.

Edited by blindowl
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4 hours ago, bibilit said:

Hard to say without another drive side by side. 

Probably an issue with the drive (board)

is the drive spinning freely by hand ? Belt still there ?


Yeah, belt is there and it spins if I move it by hand. My first thought when it started working (briefly) was that it came to life after I moved the belt/motor (after being still for 30 years...). I've tried that again but no luck. And the load-from-audio method I described actually causes the disk spin, so the motor/belt seems fine.

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I think it's fixed now. One of the transistors on the interface card looked kinda strange. Upon closer inspection, I could see that the component had been replaced at some point. And the PCB had been slightly damaged during the replacement. I removed the transistor, cleaned the card and put it back again. And now the device starts up again. Hopefully it will last longer than overnight this time ...

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