Disk drive missing only sometimes.

issalig · 20:49, 27 September 22

I have a 3" disk drive (EME-155) in a CPC6128 that the first time (let's day cold start) it gives
"Drive A: disc missing:"

Then I just press R for retry and it works ok.
The following accesses to disc are ok but when it is stopped for some time it says disc missing, again.

I have changed the belt because I was thinking it was a problem of grip but with the new belt (that works good in other drive) it has the same behaviour.

Also I have check other disk drive in this 6128 and it is working ok, so I discard it is a problem from the 6128.

Any idea?

Jean-Marie · 21:04, 27 September 22

Have you measured its RPM ? It should be around 300.
https://www.cpc-power.com/index.php?page=detail&num=10029

issalig · 22:18, 27 September 22

No, I have not checked RPMs, becausein the second attempt it works, so I guess RPMs are ok.

[SOLVED]
I have realized that the IR sensor that in EME-155 is a small pcb on the front top it was not aligned to the hole. Now, I have moved the pcb a little bit (it has a screw to ajust the position of the pcb) and now its working.

What it is interesting is the mechanism, that after a retry it seems to ignore the ir sensor and it just reads the disc. Not sure if this behaviour is in ROM or disc controller.

issalig · 12:10, 29 September 22

Ok, this is done in amsdos ROM

http://cpctech.cpc-live.com/docs/amsdos.asm at &c903

issalig · 21:51, 10 October 22

[NOT YET SOLVED]

It still fails. I have measured the voltage in the sensor and it is 4.5V when the disc is inside and 0.75V without disc. So, that menas light is arrivinga and I would say sensor is working ok but there should be something more because it is still saying Disc missing and then after "R" for retry it reads the disc and the next time it reads again "Disc missing" and then "R", ...

Any idea what's failing?

Bryce · 08:01, 11 October 22

So you still haven't checked the RPM's?

Bryce.

issalig · 11:09, 11 October 22

I have now checked them, it is 293.5 which I would consider ok.

Anyway I did adjust the screw to "300.1" but still has the same behaviour

Bryce · 12:40, 11 October 22

Have you cleaned the read/write heads?

Bryce.

issalig · 15:47, 11 October 22

Yes, and still the same

First, I thought it could be due to the phototransistor, but given that rpm are reported I assume phototransistor is ok (If I cover the red led with a paper rpm are not correct which it also correct)

panosr · 22:30, 20 November 22

hey, it seems you need to align the track step mechanism.

All credits should go to Noel's Retro Lab which shows the procedure here:

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Disk drive missing only sometimes.