Commodore 1571 Disk Drive Flash Green LED

[slaanesh]

Hi everyone

I've got a Commodore 1571 disk drive that's not working correctly.

 

On power up the red LED lights up as does the green. There is brief activity and then the green LED goes off. It looks normal so far.

Inserting a disk means that the motor starts up briefly and then stop again. Same when removing so the write sensor is working. It looks like the Track 0 sensor is also working.

Not sure about the index sensor - how to test this one?

 

Trying to get a directory LOAD"$",8 says "FILE NOT FOUND" followed by a flashing green LED.

 

Initialising the drive does the same OPEN 15,8,15,"I":CLOSE 15. The head moves back and the forth and then stops with a flashing green LED.

 

I've cleaned the heads, they are perfectly fine and clean. I've measured resistance on each head - it ranges from about 10.1 Ohms to about 13 Ohms - most measurements are the former.

I've cleaned the read head rails, they are pristine and have a small amount of lube. The head glides easily.

I've replaced the CPU board with a known good one, all tests are the same. I think my original CPU board is also fine.

I've measured voltage from the power board, it's spot on 11.96V even with load ie. drive running and spinning. The other voltage is 4.98V so also good.

I've changed all the caps on the motor board (desperation); no change.

The read head looks good and level; the drive has been stored with the disk protector and the drive lever in the down position.

 

I've tested on various commodore computers:

On my C128 same thing happens, as with on my C64 and my Vic20.

On the C128 I PRINT DS$ and it says 27,READ ERROR 18

 

I have a scope, multimeter, working VIC-1541 and C 1541-II.

I've got working disks that I've formatted and can read from my other drives. It doesn't even matter, like I said, doing the initialise results in the flashing green LED.

 

Any suggestions?

It's pretty frustrating.

[Shadowfire]

Note that the index hole sensor isn't even used unless you are using CPM formatted disks that require index synchronization.  GCR / 1541 / native 1571 mode disks do not use the index sensor, they establish synchronization with a special pattern in the data stream that the hardware can detect.

[slaanesh]

In the mean time I create a 1541 test cartridge from World of Jani and did an alignment test.

It failed miserably. 

The 1571 cannot even read a single track. Could it be the alignment is that much out physically?

 

Where to go from here?

 

See the two photos, ran the test a few times here are a couple of the results.

Edited June 16, 2022 by slaanesh

[nadir]

Following.  I just picked up a C-128D that has this same issue with the internal drive.

[slaanesh]

My next task is to check on my scope what sort of activity exists on the lines going to the head whilst the drive is actively reading.