I recently came across two 800K Sony floppy drives where the disk was not ejecting. I replaced the gear which is known to break, but the eject motor just wouldn't engage. After some troubleshooting, cause of issue was a failed transistor.
Background
I've had one floppy drive (MP-F51W-23) laying around which I recalled something didn't work right, but never really looked into it as it was a spare.
I recently got my hands on an Apple IIc Plus which uses the same 800K MP-F51W-23 Sony floppy drive. After replacing the bad gear and fixing some cold solder joints on the eject motor, I still had issues with ejecting. The eject motor would only engage if I manually turned the gear away from the home position. The eject button on the IIc+ didn't do anything, I then noticed that my spare drive had the same issue. I pulled a known working Sony drive to narrow down the issue, and it came down to the logic board on the floppy drive. Both my spare and the IIc+ floppy drive has the same issue.
Diagnostic
Since the issue was with the eject mechanism, I started comparing the non-working floppy logic board with a working one starting from the eject motor pins. I quickly noticed that two of the eject motor pins were shorted, and the short came from transistor Q7. On one board the transistor was labeled "BV3" and "BV4" on the other.
Scouring the internet, I didn't find anyone reporting this transistor failed, which was surprising to me as I had two drives where this transistor failed. I did however notice some people reporting the issue of the eject not working and having similar symptoms to mine. One thing to note is that I did most of my testing on the IIc+, I don't fully recall, but I did plug in the non working drive to the Mac Plus for a brief moment and I think instead of not ejecting it may have been suck on continuously electing, I don't fully recall.
Repair
The transistor labeled BV4 is a transistor part number 2SB624. I ordered a 50 pack of NEC old stock as it was pretty cheap and had fast shipping.
After replacing the transistor, the eject motor works perfectly. So if you're having issues, with your drive, check Q7 for shorts.
I think the cause of the failed transistor is the motor continuously running when the gear fails. The drive wasn't designed to continuously run the eject motor, and I notice it gets really hot when running for just several seconds. If the gear fails in such a position where the eject is continuously engaged and running, the transistor could fail.
I do have a lot of extra transistors. If anyone has a such a failure, you can message me and I can get one mailed in a regular letter (note I'm in Japan so shipping could take a week or two).
Background
I've had one floppy drive (MP-F51W-23) laying around which I recalled something didn't work right, but never really looked into it as it was a spare.
I recently got my hands on an Apple IIc Plus which uses the same 800K MP-F51W-23 Sony floppy drive. After replacing the bad gear and fixing some cold solder joints on the eject motor, I still had issues with ejecting. The eject motor would only engage if I manually turned the gear away from the home position. The eject button on the IIc+ didn't do anything, I then noticed that my spare drive had the same issue. I pulled a known working Sony drive to narrow down the issue, and it came down to the logic board on the floppy drive. Both my spare and the IIc+ floppy drive has the same issue.
Diagnostic
Since the issue was with the eject mechanism, I started comparing the non-working floppy logic board with a working one starting from the eject motor pins. I quickly noticed that two of the eject motor pins were shorted, and the short came from transistor Q7. On one board the transistor was labeled "BV3" and "BV4" on the other.
Scouring the internet, I didn't find anyone reporting this transistor failed, which was surprising to me as I had two drives where this transistor failed. I did however notice some people reporting the issue of the eject not working and having similar symptoms to mine. One thing to note is that I did most of my testing on the IIc+, I don't fully recall, but I did plug in the non working drive to the Mac Plus for a brief moment and I think instead of not ejecting it may have been suck on continuously electing, I don't fully recall.
Repair
The transistor labeled BV4 is a transistor part number 2SB624. I ordered a 50 pack of NEC old stock as it was pretty cheap and had fast shipping.
After replacing the transistor, the eject motor works perfectly. So if you're having issues, with your drive, check Q7 for shorts.
I think the cause of the failed transistor is the motor continuously running when the gear fails. The drive wasn't designed to continuously run the eject motor, and I notice it gets really hot when running for just several seconds. If the gear fails in such a position where the eject is continuously engaged and running, the transistor could fail.
I do have a lot of extra transistors. If anyone has a such a failure, you can message me and I can get one mailed in a regular letter (note I'm in Japan so shipping could take a week or two).
