EME-150A Read Error

[eto]

So I have serviced 6 drives over the last 2 days. 4 came out fine after cleaning, replacing the belt and some grease. One finally made it, after some advice here in the forum (not removed old belt leftovers properly) - but the last one still has an error:

I have one EME-150A which responds with a Drive Error, when I try to read the directory. It rotates at 300RPM perfectly and I can see the stepper motor working.

Based on what I have read here and what I have seen in Noels videos, I could imagine that the head is not aligned. However I can't find any information on how it's done on the EME-150A. Would be great if someone has an idea what I can do with the EME-150A - or if it's possible at all.

[simondo]

The service manual for the 6128 and DDI-1 (which includes FD-1) details the alignment procedures. It requires a test disk and oscilloscope to adjust positioning, index timing, head output, head azimuth.

Service manuals here:
https://www.cpcwiki.eu/index.php/Service_Manuals

Bryce is the expert.

[SerErris]

Can the test disk be written with a normal 3" drive? Or ist it a special disk, that cannot get written, because the drive cannot write the sector format or anything?

[eto]

As far as I know, there is no such test disk in existence any more.

[pelrun]

It's definitely not possible to write a useful test disk with a standard drive - it has tracks at non-standard positions and a track where the magnetic alignment varies along it's length. As a consumer drive has only a fixed head and track stepping, those analogue features are not replicable.

[SerErris]

Okay, that is what I thought. However for the alignment a normal disk and a test program is "good enough" if you do have an oscilloscope and some patience. ... 

I assume that those disks do not exist anymore and cannot get created anymore as well?

[Bryce]

I usually use an original game disk, as these were written on calibrated drives. However, I have other bad news. The EME-150A used a different head motor which is known to wear out and they can rarely be re-aligned once this has started happening.

Bryce.