EME-156 motor not spinning, how to troubleshoot ?

Started by reno, 19:13, 19 March 23

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

reno

Hi,

I've just changed the belt on an EME-156, but I should have first checked that the drive motor was spinning ! It isn't unfortunately.
I'm testing with a Greaseweazle that works fine with another 3" drive.
I don't think it's a power issue, as the stepper motor is working (even if I get a loud noise when reaching track 0, need to solve that separately).

I have 0V at CN3 (where this motor connects to the board), even when sending commands that should make the drive spin. I did disconnect this while servicing the belt, so it's possible it may have broken, but it doesn't look like it.

Any tips for troubleshooting ?

Thanks

Bryce

Stepper motor = 5V supply, Rotary motor = 12V Supply. The power socket to the drive should have both 5 and 12V at all times, even when nothing is spinning / moving. If the 12V rail is missing, then either the monitor isn't outputting 12V, the 12V cable is broken or one or both of the two transistors on the mainboard is/are fried. If there is 12V getting to the connector you may have dry joints on the drive PCB.

Bryce.

reno

Thank you.
I think something was wrong with my external setup because it started working reliably once inside the CPC.

I did have to realign the head, my first time doing this but the threads here helped a lot !
I still have a few questions :
- The motor screws were fixed in red varnish, yet the alignment was off, I had to break the varnish to fix it. How can that happen ?
- The best I could do while measuring TP2 with my scope was ~180mV Vpp. That was enough to read most disks, but I've seen that it should be way more than that ?
- The adjustment range was limited to about 90°, on one end by wires getting stopped by the board, and on the other by a piece getting stopped by a screw. I didn't try too hard, but should I be able to rotate it 360° to find a better position ?
- If I didn't hear any drilling noise when doing a "cat", does that mean I don't need to worry about the track 0 sensor ?

Bryce

To answer some of those:

- The motor screws were fixed in red varnish, yet the alignment was off, I had to break the varnish to fix it. How can that happen ? 
Because moving parts wear down and the amount of wear needed is tiny.

- The best I could do while measuring TP2 with my scope was ~180mV Vpp. That was enough to read most disks, but I've seen that it should be way more than that ?
Where did you see higher values? The Amstrad documents state no less than 140mV.

- The adjustment range was limited to about 90°, on one end by wires getting stopped by the board, and on the other by a piece getting stopped by a screw. I didn't try too hard, but should I be able to rotate it 360° to find a better position ?
The entire adjustment range is only around 45°, after that you are overlapping the same calibration point.

- If I didn't hear any drilling noise when doing a "cat", does that mean I don't need to worry about the track 0 sensor ?
If it can CAT a disk the track 0 sensor doesn't need to be touched.

Bryce.

Powered by SMFPacks Menu Editor Mod