tezza
Veteran Member
Another disk drive adventure (and yes I have read the sticky).
I think I know what happened to these drives but I’d like to know exactly what’s wrong, even if it might be hard to fix. Someone out there might know.
The Apple haul left me with a total of six Disk II-type drives. Of the drives, three worked, one I got working (speed alignment), and the other two were broken. Two of the four working drives were nice TEAC models.
One of these TEAC drives stopped working a while ago. The disk would spin but wouldn’t recognise, read or write to any disk. Yesterday I had a close look at this drive with aim of finding out what’s wrong.
Having a working drive, I thought I’d try to isolate the problem by swapping the cables and circuit boards one at a time between the two drives. Doing this revealed the problem was most likely on the main circuit board, as a board swap fixed the broken drive.
Photo 1: Drive from bottom showing main (green) circuitboard
However, as I was doing some more testing, the second drive suddenly failed and exhibited exactly the same symptom as the first? I found that not only do BOTH drives now fail to recognize disks but it you use them to boot good disks, they usually corrupt them!
What do I think is wrong? My theory regarding both drives is that the disk index timing light is no longer working. I deduced this because…
First reason. When I’ve pulled away the sensor board (but left all its cords attached) I can’t see any light at all through the index hold when the disk is spinning, or when a drive tries to boot WITHOUT a disk inserted. The disk index timing bulb should be lit, yes?
Photo 2: Index hole sensor
Photo 3: Index hole sensor circuit board removed showing timing light (upper right)
Second reason. A piece of software I used for tuning disk timing, doesn’t work at all for the two faulty drives. They spin, but there is no timing registered (see photos). On a good drive, timing is registered just fine. I figure the disk index timing light is used to determine speed (am I correct in assuming this?).
Photo 4: Timing software on a working drive.
Photo 5: Timing software on a non-working drive (no speed indicator appears)
How has this happened and what exactly is wrong? I don’t know exactly what’s wrong I have a suspicion as to what might have caused it. At one stage during the testing yesterday I accidently plugged in the drive incorrectly. It’s really easy to do this with the Apple II disk controller, putting the plug in the wrong layer of pins. I should have listed this in the list of design flaws.
Photo 6: Opps. How NOT to plug in a Disk II to a Disk II controller card
Now I’m not sure if this caused the second drive to fail or not as I was juggling a few things at the time. But it was soon after that I noticed it had gone the same way as the first one! And, when I think of it, the reason that FIRST drive may have stopped working is that I’d done the same thing a few months ago. I remember doing it once before (I know, slow learner) and although I didn’t directly connect the dots at the time, it could have been that mistake that zapped the first TEAC.
So, my theory. Through incorrect plugging on both drives, I’ve zapped something on the circuit board which controls the disk index timing light. With the light not functioning, the drive doesn’t recognise a disk is present.
Do these deductions seem reasonable and if so, does anyone know EXACTLY which IC or component might be damaged?
Tez
I think I know what happened to these drives but I’d like to know exactly what’s wrong, even if it might be hard to fix. Someone out there might know.
The Apple haul left me with a total of six Disk II-type drives. Of the drives, three worked, one I got working (speed alignment), and the other two were broken. Two of the four working drives were nice TEAC models.
One of these TEAC drives stopped working a while ago. The disk would spin but wouldn’t recognise, read or write to any disk. Yesterday I had a close look at this drive with aim of finding out what’s wrong.
Having a working drive, I thought I’d try to isolate the problem by swapping the cables and circuit boards one at a time between the two drives. Doing this revealed the problem was most likely on the main circuit board, as a board swap fixed the broken drive.
Photo 1: Drive from bottom showing main (green) circuitboard
However, as I was doing some more testing, the second drive suddenly failed and exhibited exactly the same symptom as the first? I found that not only do BOTH drives now fail to recognize disks but it you use them to boot good disks, they usually corrupt them!
What do I think is wrong? My theory regarding both drives is that the disk index timing light is no longer working. I deduced this because…
First reason. When I’ve pulled away the sensor board (but left all its cords attached) I can’t see any light at all through the index hold when the disk is spinning, or when a drive tries to boot WITHOUT a disk inserted. The disk index timing bulb should be lit, yes?
Photo 2: Index hole sensor
Photo 3: Index hole sensor circuit board removed showing timing light (upper right)
Second reason. A piece of software I used for tuning disk timing, doesn’t work at all for the two faulty drives. They spin, but there is no timing registered (see photos). On a good drive, timing is registered just fine. I figure the disk index timing light is used to determine speed (am I correct in assuming this?).
Photo 4: Timing software on a working drive.
Photo 5: Timing software on a non-working drive (no speed indicator appears)
How has this happened and what exactly is wrong? I don’t know exactly what’s wrong I have a suspicion as to what might have caused it. At one stage during the testing yesterday I accidently plugged in the drive incorrectly. It’s really easy to do this with the Apple II disk controller, putting the plug in the wrong layer of pins. I should have listed this in the list of design flaws.
Photo 6: Opps. How NOT to plug in a Disk II to a Disk II controller card
Now I’m not sure if this caused the second drive to fail or not as I was juggling a few things at the time. But it was soon after that I noticed it had gone the same way as the first one! And, when I think of it, the reason that FIRST drive may have stopped working is that I’d done the same thing a few months ago. I remember doing it once before (I know, slow learner) and although I didn’t directly connect the dots at the time, it could have been that mistake that zapped the first TEAC.
So, my theory. Through incorrect plugging on both drives, I’ve zapped something on the circuit board which controls the disk index timing light. With the light not functioning, the drive doesn’t recognise a disk is present.
Do these deductions seem reasonable and if so, does anyone know EXACTLY which IC or component might be damaged?
Tez