modified sony MPF920 floppy drive issue

[Traindriver69]

Hi all
I brought a couple of new old stock sony MPF920 drives ages ago I modified one and put it in my amiga 1200 no issues but recently I brought an amiga 500 with a faulty floppy so I thought excellent time to bring the other one out to use.
I modded it and worked straight away I then put everything back together and would not read disks I took it apart and found that the cable from the bottom of the two pads to the top pad below the small ribbon cable had come away at that point so I resoldered it and still it will not read disks.
the drive clicks put a disk in and the head travels to its full extent and moves a couple of times and get a white screen on the tv.
I put the faulty amiga drive in which would sometimes load disks and that still loads disks sometimes so not an issue with the amiga.
Is it possible that the loose wire has shorted something any advice would be much welcomed.
Many Thanks

[solarmon]

Pictures of the mod and the faulty pad/wire would help explain your issue.

Does the modded drive from the A1200 work in the A500?

[Traindriver69]

Hi
yes now tried the 1200 drive and its working and it was the green wire at the top that came detached.

[Franchute13]

Do I try to repair the original unit?
If I clean the heads and the problem continues, you should try changing the capacitors.
more info:
http://eab.abime.net/showthread.php?t=71760

[Traindriver69]

I no longer have the original unit so need to try and get the Sony one working.

[solarmon]

Did you cut the trace to pin 34? It's not obvious that has been done in your picture.

[Traindriver69]

Hi yes the track has been cut

[solarmon]

Have you checked continuity - to make sure that there connectivity to where it should have and that there are no shorts to where it shouldn't have.

I would load up Amiga Test Kit with the working drive or with a Gotek drive, swap it out with the suspect drive and test the floppy drive signals to see what is working or not working.

[Traindriver69]

Here are the signal test and read test results it also failed on the write test

[solarmon]

If you press F1, does the heads seek in and out?
If you keep pressing F6, does it come in and out of TRK0
If you press F5 to turn the motor on, do you get index pulses incrementing (you will need a floppy disk inserted)?

Looks like you got an old version of ATK - download the latest from

https://github.com/keirf/Amiga-Stuff

The you can also test manual stepping in and out.

Also, use the alignment test with a good known AmigaDOS formatted disk. The drive needs to be aligned to be able to read and write properly.

You can also test whether alignment is the issue by using X-Copy to format a disk and to read it back. If that is OK but you can't read other known working disks then that suggests alignment issue.

[Traindriver69]

I will try this but I am still pretty sure there be some damage caused by the wire coming away as it was working fine before wire comes away and stops reading disks I replace the wire and still will not read disks and as that wire comes from pin 2 which reads disks I am wondering what it may have shorted out.

[Traindriver69]

F1 yes heads seek in and out F6 yes F5 the impulse numbers do rise also ran disk read with new version

[solarmon]

What does the alignment test show, for tracks 0, 39 and 79?

[Traindriver69]

Hi
Here are the results

[solarmon]

To me that suggest that it is getting read data - there are "+" characters on the lower head. So it might still be alignment issues.

Have you check continuity of pin 2 to make sure the read data signal is getting all the way to the controller chip.

I would still do the X-Copy format and CheckDisk test. If that formats and reads back OK then it is definitely an alignment issue.