Strange problem with 1040 ST disk drive

[TGB1718]

Thought I would update this, I checked all the signals to and from the floppy drive and all seemed ok but no

joy reading floppy's or a GOEX drive, this was on my 520STM.

 

I decided to do the mod here https://www.exxoshost.co.uk/atari/last/DMAfix/index.htm

I ordered some 10K resistor packs and fitted one to my 520 although I didn't attach them to

the IC legs as shown just in case I damaged the chip, I located the correct pins from the underside of the

board and laying the pack flat, I soldered each leg to the legs sticking through the bottom of the board.

 

Powered up, still problems with the floppy, but my hard disk booted very quickly, before it seemed to

keep trying to boot from the floppy, I tried a few different floppy disks and found most would read ok,

I coppied whole floppy contents to a hard drive partition, ran the copied programs and they worked

fine, just bad luck the first floppy I tried was a bad one. I had tried these other ones that worked

before the mod and none would read.

 

So many thanks to @exxos for your hard work in determining the problem with our ST's.

 

Now back to do my 1040STFM and hope it's the same problem

[TGB1718]

Quick update, bit premature, it still doesn't use the GOEX nor most floppy disks, changed the FDC and 7406 chips, but still same problem,

will read some disk directories, but not load/access any files or sub-directories, except just one disk with a few files on it.

 

Just had a thought while typing this,? maybe the disk it accessed is an old single sided disk, I use that with my 520 for quite a while.

In which case maybe the problem is the side select line (grasping at straws now)  something to try tomorrow.

[TGB1718]

This morning I attached a normal floppy drive and having a look at any floppy disks that may be single sided, then

I can across my original Starglider disk, I know this was an early program for the ST and knew most early

games came on single sided disks.

 

I put this disk in and booted the ST and although I still have the slower 1770 FDC fitted, it booted first go and the

game played, so it looks as I previously suspected it's the Side select thats faulty, going to get my scope on it

next and hope it's just a faulty solder joint or track otherwise it's the YM2149 chip and it's not socketed

[ParanoidLittleMan]

Yeah, it can be YM chip - drive and side select lines are vulnerable - no buffering/amplifying . I managed to damage mine when attached 5.25 inch floppy drive, what loads those lines more than 3.5 inch drives. Not recently, was some 32 years ago.

[TGB1718]

Ordered 2 today for around £10, I'm assuming whatever broke my 520 did the same to my 1040 as it

shows the same issue, just need to try a single sided floppy in it to confirm.

 

1 hour ago, ParanoidLittleMan said:

I managed to damage mine when attached 5.25 inch floppy drive

Interestingly I used to have a 5 1/4 drive on my ST's for years with no problems, one I attached to my external floppy

by putting in a double ribbon cable, but I later bought a second external 5 1/4 ST floppy drive (can't remember the make),

but it never worked, maybe thats what caused the problem.

[ijor]

10 hours ago, TGB1718 said:

I put this disk in and booted the ST and although I still have the slower 1770 FDC fitted, it booted first go and the

game played, so it looks as I previously suspected it's the Side select thats faulty, going to get my scope on it

next and hope it's just a faulty solder joint or track otherwise it's the YM2149 chip and it's not socketed

 

As Pera said, the PSG ports are very fragile and they are known to get damaged quite easily. It would be strange that you had the same issue at both computers, but it is conceivable I guess.

 

7 hours ago, TGB1718 said:

Interestingly I used to have a 5 1/4 drive on my ST's for years with no problems

It depends on the specific 5.25 drive. Some work fine, depending mostly on the pullup resistors. The older the more dangerous because they sometimes have very strong pullup resistors. Of course that drives designed specifically for the ST are just fine, except that they require a slower step rate.

[TGB1718]

13 minutes ago, ijor said:

Of course that drives designed specifically for the ST are just fine, except that they require a slower step rate.

The one that didn't work was designed for the ST, with normal 14 pin cable (supplied), internally it's an older type

with edge connectors to the drive board

[ijor]

7 minutes ago, TGB1718 said:

The one that didn't work was designed for the ST, with normal 14 pin cable (supplied), internally it's an older type

with edge connectors to the drive board

Yes, I understood. My point was just about the pull up resistors. Don't know why yours didn't work, but likely it was for a different reason.

 

Btw, I recommend to put back the WD1772 when you can. Even when the WD1770 should mostly work fine. The different timing might affect some copy protections.

[TGB1718]

8 minutes ago, ijor said:

Btw, I recommend to put back the WD1772 when you can. Even when the WD1770 should mostly work fine. The different timing might affect some copy protections.

Sure will, only bought the 1770 to check if the FDC was ok or not, 1772 was a silly price, but if it had been faulty, I would have had to buy one

if original disks didn't load.