DDI-1 - Is the drive repairable?

[Chinnery]

Sometimes, I wish I hadn't started getting back into the Amstrad CPC. It's taking up so much of my time
Fortunately, I've had a really good rate of repair on these "Not tested" Amstrad bits I've been hording, so it's time well spent on the whole.
I have, however, met my match. A 3" floppy drive which doesn't want write beyond track 0. The history of the drive from when I received it was that the obvious drive belt issue, also the stepper motor was very clunky when seeking across the drive. I've sorted those out but later found I needed to adjust the rotation speed (it was ~290rpm, it's now ~299rpm) - as close as I can get.
Now it reads all (both) disks I've used with it, one a retail release, the other formatted on my other drive, however it won't write beyond track 0. It will format and verify on track 0, but when trying track 1, I just get a write error.
The drive itself is an early model, the EME-150A, so it's not a write protect pin missing. As I've mentioned, I've changed the belt and given it a really good clean and applied ample lithium grease where needed. The "pressure" felt pad looks good. The speed is good. I'm now stuck.
Beyond a multi-meter, I don't have any diagnostic tools. Is there any hope for me, or at least for the drive?

[tjohnson]

That is strange, have you tried calibrating it.  Loosen the screws and rotate the motor a tiny fraction and try again, you might get lucky but its strange that it reads disks but won't write so I suspect that won't work as it would struggle to read disks.  Cleaned the head? 

[Shaun M. Neary]

Paging Doktor @Bryce , Paging Doktor Bryce!

[Chinnery]

That is strange, have you tried calibrating it.  Loosen the screws and rotate the motor a tiny fraction and try again, you might get lucky but its strange that it reads disks but won't write so I suspect that won't work as it would struggle to read disks.  Cleaned the head?

The EME150a doesn't have much room for physical re-calibration - if any. Everything seems quite precisely bolted in place.
Yes, head has been cleaned.

[tjohnson]

I think you will be able to loosen the screws holding the motor that drives the worm drive and rotate it, you shouldn't really need to though.

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[geeb]

I have replaced the belts on two DDI and the only issue I had with both units was the ribbon interface connector on the back of the 464. I just went at the thing with a stiff brush and that cured it. Sometimes now I can get a lock out if I leave the 3" in the drive when powering down. I just make sure I fully retract the disk before switching off. Never leave the disk in the drive, that causes me problems also on the PCW8256.

By the way I have a 3" head cleaner that seems to work.

http://www.scuzzscink.com/amiga/scuzzblogdjul17_2803.htm

scuzz

[Bryce]

Paging Doktor @Bryce , Paging Doktor Bryce!

Let me just finish this chunk of Turkey and I'll be with you....

Ok, that's not a problem I've seen before. Is the head physically stepping to Track 1 when it tries to write to it?

Have you checked for breaks in the wires to the heads? It may be loosing the connection as soon as it moves away from Track 0?

Back to the Turkey...

Bryce.

[Chinnery]

Let me just finish this chunk of Turkey and I'll be with you....

Floppy drives should never, ever interrupt turkey scoffing


Things have moved on a bit since my original post, but yes, the head would step to track 1 then get the write error. The broken wire may be a possibility however...


Today, as I have finally got a bit of free time, I had another look at the drive. As mentioned here about nudging the stepper motor to "calibrate" the drive, I took the whole stepper assembly out, mainly to ensure the threads were clear of all nasties. It was. I bobbled the spinner motor out to have a real good look at the spindle to make sure it was totally clean. It was.


I've now reassembled the drive and no longer get write errors. Yay!.... Progress.


However, if I save a file to disk, the drive goes through the motions of saving, but nothing happens...


Progress Denied.


I've just had the board off again to ensure I've got all wires in the right place, reassembled it and the same - it goes through the motions of writing without actually writing. It's still reading fine though, and if I write protect a disk, I get the correct error.


One possibility could be the head connection cable to the PCB? There is no markings that marry up which way round the cable goes. I'm assuming that if its reading then this cable is the correct way round?


https://www.dropbox.com/s/iavj2mjn43gc0wh/2017-12-26%2012.51.07.jpg?dl=0


And does anyone know why hat transistor is bolted to the motor? It's a nuisance having to unbolt it all the time... but it does look like the designers went out of their way to put it there...

[Bryce]

They used the metal casing of the motor as a heatsink. While you are experimenting/repairing it can be left hanging in the air.

Bryce.

[Chinnery]

Ok. Finally got to the bottom of this. The short answer was: The heads were connected the wrong way round.
Not being able to get to the bottom of this, I decided to re-open my working drive and swap boards, at least that way I would have a better idea if the problem was mechanical or electrical.
When I'd finally got through to the last connector - the heads to the PCB (CN1), I noticed that on the working drive, there was a sticker holding the connector in place - something missing from the broken drive. I also noticed that the broken drive was connected back to front.





So, the first problem, as Bryce mentioned, was probably the loose connector. No tape holding it together as one meant that over time, it had worked a bit loose - enough for track 0 to be writable, track 1 to not, or something along these lines.


The second problem was almost certainly me, connecting the cable the wrong way round. On the broken drive, there was a white mark on the connector which I had assumed was pin 1... nope. The strange thing was that when wrong, the drive read fine.


Anyway, just if someone else needs the info, attached in an image of how the connector should be orientated.

[tjohnson]

Excellent good result!

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