A500 Strange Floppy Drive Issue

endangermice · 19 July 2019, 10:30

Morning everyone, hope you're well.

I was wondering if any of you have any advice on a bit of a strange issue I'm seeing with an A500 (rev 6) I bought a few months ago. The issue is that it won't read discs properly. Some discs it won't even read the boot sector whereas others e.g. a Workbench disc will try and boot but fail with a read error half way through the boot sequence (retrying doesn't help). What makes this case odd is that it isn't a problem with the drive. I have tried the A500 drive in my A1200 and it reads discs fine. If I try the A1200 drive in the A500, it fails to read discs in exactly the same way.

I have recapped the A500, tried the floppy cables from the A1200, reseated the chips (particularly Paula as she is responsible for controlling the drive), swapped the odd and even CIA (to see if that would make a difference) and have visually checked the board.

Does anyone else have any suggestions? I have a Vampire card from the wonderful Apollo team on it's way so moving forward this might not be so much of a problem (as I will be use an sd card prepared with WinUAE to install software etc). It would be good to get this Amiga reading discs properly and I would like to solve the mystery.

My hunch is that there could be a problem with either one of the logic chips or with Paula or a broken or damaged trace that I have missed. Before I dig out the schematics, I thought I'd ask to see if anyone seen this type of problem before and if you have do you have any pointers as to what I might check?

Many thanks,

Damien

cmorley · 19 July 2019, 10:51

Have you cleaned the drive heads?

endangermice · 19 July 2019, 17:22

The main drive in the A500 is a brand new modified Sony 920MPF floppy drive which works just fine in the A1200, also the original A1200 drive works just fine in the A1200 but fails in exactly the same way in the A500 so it is nothing to do with the heads as both drives work in one machine but not the other.

Thanks for the suggestion though.

cmorley · 19 July 2019, 18:20

Sorry. Read the title & must have glossed over the bit where it isn't a drive issue.

DofD · 19 July 2019, 19:13

Hmm... Interesting issue. I would suggest checking the Paula socket for any cold solder joints. I'd also check the floppy connector on the motherboard to make sure there are no broken solder points.

Also, copper oxidation on the floppy connector pins can cause issues.

Is there any difference if the 500 is warm or cool? Issues with a cracked trace may come and go as the board heats and cools.

19 July 2019, 10:30	#1
endangermice Registered User Join Date: Jan 2019 Location: Cheltenham Posts: 4	A500 Strange Floppy Drive Issue Morning everyone, hope you're well. I was wondering if any of you have any advice on a bit of a strange issue I'm seeing with an A500 (rev 6) I bought a few months ago. The issue is that it won't read discs properly. Some discs it won't even read the boot sector whereas others e.g. a Workbench disc will try and boot but fail with a read error half way through the boot sequence (retrying doesn't help). What makes this case odd is that it isn't a problem with the drive. I have tried the A500 drive in my A1200 and it reads discs fine. If I try the A1200 drive in the A500, it fails to read discs in exactly the same way. I have recapped the A500, tried the floppy cables from the A1200, reseated the chips (particularly Paula as she is responsible for controlling the drive), swapped the odd and even CIA (to see if that would make a difference) and have visually checked the board. Does anyone else have any suggestions? I have a Vampire card from the wonderful Apollo team on it's way so moving forward this might not be so much of a problem (as I will be use an sd card prepared with WinUAE to install software etc). It would be good to get this Amiga reading discs properly and I would like to solve the mystery. My hunch is that there could be a problem with either one of the logic chips or with Paula or a broken or damaged trace that I have missed. Before I dig out the schematics, I thought I'd ask to see if anyone seen this type of problem before and if you have do you have any pointers as to what I might check? Many thanks, Damien

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19 July 2019, 10:51	#2
cmorley Registered User Join Date: Jun 2018 Location: Oxford, UK Posts: 66	Have you cleaned the drive heads?

19 July 2019, 17:22	#3
endangermice Registered User Join Date: Jan 2019 Location: Cheltenham Posts: 4	The main drive in the A500 is a brand new modified Sony 920MPF floppy drive which works just fine in the A1200, also the original A1200 drive works just fine in the A1200 but fails in exactly the same way in the A500 so it is nothing to do with the heads as both drives work in one machine but not the other. Thanks for the suggestion though.

19 July 2019, 18:20	#4
cmorley Registered User Join Date: Jun 2018 Location: Oxford, UK Posts: 66	Sorry. Read the title & must have glossed over the bit where it isn't a drive issue.

19 July 2019, 19:13	#5
DofD Registered User Join Date: Jun 2018 Location: Victoria, Canada Age: 56 Posts: 134	Hmm... Interesting issue. I would suggest checking the Paula socket for any cold solder joints. I'd also check the floppy connector on the motherboard to make sure there are no broken solder points. Also, copper oxidation on the floppy connector pins can cause issues. Is there any difference if the 500 is warm or cool? Issues with a cracked trace may come and go as the board heats and cools.

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