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IBM 5150 showing 601 error after POST

alejack12001 said:
The error message that I am receiving is saying write protect error when I try to format a blank 360 KB floppy disk. The notch is not covered on the disk and in fact the floppy disk is a new disk. Could this be a a head issue or what?
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See the TM100-2 diagram at [here]. Is test point 9 behaving as expected? If always HIGH, possible problem causes include (but are not restricted to) switch and a poor P8-to-J4 connection.
 
jafir said:
On the full height drive you should be able to see the micro switch for the mechanism that enables or disables the write protect. It’s a little easier to see from the top on a tandon, and from the front on a MPI drive. Make sure that it’s not stuck up or blocked by something.

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The lever shown in the video is not in either of my two Tanon-2A. I think the switch in question may be the issue. Where is this switch on the physical drive? I found two wire headed for a small box like that is attached on the front of the floppy drive. Is that connection associated with the switch in question?
 
alejack12001 said:
The lever shown in the video is not in either of my two Tanon-2A. I think the switch in question may be the issue. Where is this switch on the physical drive? I found two wire headed for a small box like that is attached on the front of the floppy drive. Is that connection associated with the switch in question?
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Do the photos at [here] help ?

alejack12001 said:
I think the switch in question may be the issue.
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If test point 9 is behaving as expected (per post #21), then there must be a switch present, and it must be working.
 
modem7 said:
Do the photos at [here] help ?


If test point 9 is behaving as expected (per post #21), then there must be a switch present, and it must be working.
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First the pictures are very helpful as I really didn't know, which two pins oof P8 were associated with the write protect switch.

The composite picture showing the switch with the plastic trigger is where I believe my problem exists. On the good drive, the plastic arm upside down V shaped part of the arm slides into the slot in the floppy disk.The lever associated with the arm seems to pull the switch open and tells the drive that there is a writable disk there. On the drive, where I am getting the write protect error, the upside down V shaped part of the arm doesn't completely slide into the slot of the floppy disk. The arm is there but there is about 1-mm difference in height, which maybe enough to keep the switch closed instead of open. I need to measure the voltage recommended at P8 to see if its high or low, when the floppy is inserted.

If the problem is mechanical that is if the lever is bent or worn out, how would this be fixed? If the problem is electrical then another switch would be in order.
 
I adjusted one of the screws holding the switch for the Tandon TM100-2A. The adjustment allowed the arm to identify the floppy as writable seemed to cough up a new error quoting while trying to format the floppy disk with the following message: "Drive B Error writing system areas." With the original error "Write protect error" just two lines below.. I guess I'll have to follow-up with that P8 connector test to see if something else is going on.
 
After several hours of testing, I found the write-protect switch in the Tandon TM100-2A is bad. Ohmmeter and scope seemed to suggest that adjustment of the write-protect switch made no difference as the switch was open circuit. The next task is to take the TM100-2A apart and see if the switch can be replaced.
 
I have new problem as the drive belt appears to be loose. Does anyone know where I might be able to find a drive belt for the Tandon THm100-2A floppy drive?
 
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