• Updated 2023-07-12: Hello, Guest! Welcome back, and be sure to check out this follow-up post about our outage a week or so ago.

Macintosh LC II Sony Floppy MFD-75W-01G or swim problems

Madcat333

New member
Hello there,
i desperatly couldn't get my floppy drive to read disks. I've recapped the logic board and the floppy drive. After that the drive works and i could get into the system install screen. But the next day it refuses to read the install disk and it ejects it. The happy mac showed up for 1..2 seconds then it ejects it. I checked the disc on another system. It was readable just fine. I tried to align the Track 0 sensor with try and error method, but i only got the happy mac back for 1..2 seconds. Then i checked the traces and voltage ratings between the swim and the 20-pin header. Unfortunately i only found a pinout from the Apple II with a -12V line on pin 9 which the LC II does not have. I have the bomark schematic also with no pin 9 on it. What are these PH0... PH3 lines for? And is the 0.3 mV (0V) normal on PH1? I don't know if the swim chip or the floppy drive is bad. I've tried 2 Sony Superdrives with no luck.
 

Attachments

  • db19-to-idc20.jpg
    db19-to-idc20.jpg
    87.8 KB · Views: 1
  • IMG_0442.jpg
    IMG_0442.jpg
    641.8 KB · Views: 1
  • IMG_0441.jpg
    IMG_0441.jpg
    381.4 KB · Views: 1

volvo242gt

Well-known member
If both drives aren't working, then it's probably a board issue. Could be the chip itself, a rotted trace (or more), or some cap goo that got on the chip's pins.
 
Top