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Tandy 1000EX Floppy Controller Issue

D

D10D3

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Hey guys, long time listener, first time caller.
I've been working on a Tandy 1000EX and I've run into some trouble with the floppy drive. When I first got my Tandy the drive seemed to work just fine and it had no trouble booting from disks, but after a week or so the drive stopped recognizing any disk. When I attempt to access the drive it will spin the disk, but the read head doesn't seek, and after a few moments it reports a failure to read the disk.

Here is what I've tried so far:
I tried a number of different disks.
I dismantled the drive and cleaned the heads.
I built adapter cables to allow me to use non-Tandy drives and tried several, both 5.25" 320k drives and 3.5" drives with 720k disks. These all acted in the same manner as the first.
I installed a riser card in the expansion bay with an XTCF board to allow me to boot the machine without the drive and confirmed that it seems to function in all other ways.

Theories:
As much as I don't want it to be the case, I'm starting to think there could be a problem with the FD Controller on the motherboard. I dismantled the whole machine and cleaned the motherboard and I don't see any bulging capacitors or other obvious problems, but that doesn't mean there aren't any. I'm not sure where to go from here or how to diagnose it further and would appreciate any advice.
 
Try running a diagnostic on the floppy system.

CheckIt might do it. So might Dr. Hardware Sysinfo.

It sounds like you might be right about the floppy controller. Can you disable it and put a card in with a floppy controller?
 
Looking at the 1000 EX technical manual I suppose the one bright side is *if* it's the FDC it looks like it's a generic uPD765a and not integrated into one on the Tandy custom chips. So there'd at least be some hope for replacing it, if necessary?
 
Try some of the IMD testing. You should at least be able to move the heads.

I suspect it's not the FDC, but rather the buffer (usually a 7438) between the FDC and the drive, if it's an IC at all.
 
Stone said:
CheckIt might do it. So might Dr. Hardware Sysinfo.
Click to expand...
Good idea. I think I have CheckIt on my CF card so I'll try that when I get home today.

Stone said:
It sounds like you might be right about the floppy controller. Can you disable it and put a card in with a floppy controller?
Click to expand...
I'll have to see if I can find a small one to find in that little bay. I'll have to ditch either my XTCF card or my ram expander though. I love the Tandy 1000 EX but it's pretty short on expansion slots.
 
Eudimorphodon said:
Looking at the 1000 EX technical manual I suppose the one bright side is *if* it's the FDC it looks like it's a generic uPD765a and not integrated into one on the Tandy custom chips. So there'd at least be some hope for replacing it, if necessary?
Click to expand...

I have this same issue with my sx model. the only difference is that i can't write to any disk without corrupting it. i gave up on the system after i replaced the actual socketed FDC chip along with the data seperator. both of these chips were replaced and still had issues
 
Apologies for necro-posting, but I'm having the exact same issue as the OP on this 4 year old post and instead of making a new thread I figured this was a better approach.

I have a Tandy 1000ex with the Teac 55BV-75-U drives (internal and external) and they both do the exact same thing as the OP, the disks just spin but the heads don't seek. The odd part is that if I leave the computer off for an hour or so, they head seek align will happen on BOTH drives right after the post beep and it will allow me to boot into dos 2.11, sometimes I can even load an application, but after a few minutes the disk will just spin in the drive and will continue to have this problem until I leave the disk drive alone for about an hour. Once the problem starts again both drives just spin spin but the heads don't engage. These are working disk drives by the way, putting them in another computer just works.

Any new ideas in 2023 about this really weird issue? I've managed to load into ImageDisk to check if they're aligned, but all I get is more spinning when I try to access the disk.
 
Since it's heat related, you have a major lead to follow that the others didn't.
Use some freeze spray to isolate the failing component and be sure to follow up in here. This would be very valuable information.
 
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