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Floppy disk problem

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I just picked up a loaded PEB with all the standard TI cards (32K, RS232 and Disk controller) along with the original TI floppy disk (Shugart SA400L). Everything works fine except the floppy drive will not format a disk. It will read disks, copy files and even copy a full disk but will not format. Just comes up with an error "Disk Error No disk". If I install another drive using the same cabling it works fine so the problem is in the drive however I am confused as to what the issue could be as the drive does write fine. ANy ideas?

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I just picked up a loaded PEB with all the standard TI cards (32K, RS232 and Disk controller) along with the original TI floppy disk (Shugart SA400L). Everything works fine except the floppy drive will not format a disk. It will read disks, copy files and even copy a full disk but will not format. Just comes up with an error "Disk Error No disk". If I install another drive using the same cabling it works fine so the problem is in the drive however I am confused as to what the issue could be as the drive does write fine. ANy ideas?
Capacitors go bad

Likely they aren't working well enough to power the circuitry for formatting.

Also could be other components but the first thing is that.



Sent from my LM-V600 using Tapatalk

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Thanks. Just changed the one and only electrolytic cap on the drive and no change. I tried testing the drive speed with the peripheral test program and although the disk is obviously spinning, it reports 000 RPM. I again tried copying files to a formatted disk in that drive and no problems. I am not an electronics expert but formatting must utilize a different part of the circuit.

 

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0 RPM -- could that be the index sensor?
I have seen drives with bad leds on optical sensors

Sent from my LM-V600 using Tapatalk

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The index hole sensor was my immediate thought, when I read the first post. Then I continued reading and saw that you already figured it out. But perhaps not why this is the first thing to check?

The index hole is normally used only for formatting. It's to tell the drive when one turn has been completed, so that it knows where to start the track, and sometimes confirm the whole track got written before it ended. It will also align the tracks with each other.

But once formatted, the drive and controller uses the magnetic information on the disk to figure out where the tracks are, for read as well as write operations. The index hole isn't needed then.

 

Note that this is for soft sectored disks, the kind our TI uses. Hard sectored disks existed, with one hole for each sector around the disk, and an extra hole at the starting point.

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7 hours ago, apersson850 said:

The index hole sensor was my immediate thought, when I read the first post. Then I continued reading and saw that you already figured it out. But perhaps not why this is the first thing to check?

The index hole is normally used only for formatting. It's to tell the drive when one turn has been completed, so that it knows where to start the track, and sometimes confirm the whole track got written before it ended. It will also align the tracks with each other.

But once formatted, the drive and controller uses the magnetic information on the disk to figure out where the tracks are, for read as well as write operations. The index hole isn't needed then.

 

Note that this is for soft sectored disks, the kind our TI uses. Hard sectored disks existed, with one hole for each sector around the disk, and an extra hole at the starting point.

Thanks for that explanation. It does sound like the index sensor is the issue so I will check that out. Got roped into some "domestic" jobs today and probably tomorrow as well so I will let you all know what I find when I get to it.

 

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I couldn't wait so I decided to have a look this evening and found that the mount for the index sensor was broken and the receiver part was out of position. The broken part was long gone so I was able to use some hot glue to mount it back in place and it works 100% now!! Thanks for all your help and suggestions.

 

If anyone has a broken SA400L lying around I would buy the sensor mount from you.

 

 

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Learn something every day. I didn't know the index mark was only used when formatting. One time I had troubles with the write protect. I was testing after changing the drive belt, with the drive still out of its enclosure and getting random write or format fails. I finally figured out that bright room light was confusing the sensor! I turned off the ceiling light and/or laid a cardboard cover over it and all was well.

 

I'd think if the hot glue fix works, I'd leave it that way. Chances are the only way you'll score a holder bit is to snag a whole same model drive. I still have my drive stash with several SSSD TI drives from before I upgraded to double-sided, but I think they all still work. "Ran when parked" anyway. ;)

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