Floppy Drive woe's

[TGB1718]

I've been trying to get my floppy drive working on my 520STM, its an external drive, initially I got read errors 99%

of the time although the drive was detected, I read a thread on this forum that putting 10K pullups on the data lines

to the DMA controller, I did this and it improved things a bit, I can now read the directory of some disks but accessing

the files on the floppy is a bit hit and miss.

 

I also have a "real" hard drive and this works fine, absolutely no problems, which indicates the DMA chip is OK.

 

I have replaced the 1772 for a 1770 (slower step rate) FDC just to eliminate the FDC, I do appreciate the slower step

rate may cause issues with copy protected software, but just reading a directory and small text files should be fine.

With either chip I get the same sort of errors.

 

I replaced the soldered on 34 pin header in the floppy drive with a proper 34 pin plug and replaced the internal

34 pin cable to the drive, also cleaned the floppy drive heads.

 

I have tried 2 different floppy cables from the ST to the drive, still the same.

 

I have solder re-flowed the Floppy sockets on both the external drive and in the ST itself.

 

I replaced U8 the 7406 with a new one.

 

Have tried two different floppy drives (both 720K Sony models), again same results (these are the drives I have always used).

I just purchased a GOEX drive, it detects the drive, but fails to read any of the images on the drive

(all the images load fine under SteemSSE), the drive itself led lights, track/sector display seeks, but

fails every time, tried 3 different SD cards (just in case).

 

The last thing I did after "scoping" the read line which looked a bit strange (but the same on every drive) was

to put a buffer chip between the drive and the Read line of the FDC just to see if it would clean it up a bit, although

the signal looks fine, the response from the drive is still the same.

 

I'm running out of ideas, just wondering if anyone else has come across this problem and maybe can offer some

help in resolving the issue.