ThinkPad 770z - bad external floppy port?

[Edward Mendelson]

Further adventures with the 770z. I have one very good-looking one, and a battered one. Here's the current problem:

On the battered one, an external floppy works perfectly (it's the internal 1.44 drive module, connected with a cable to the FDD port on the back). When the FDD is connected to the external port, the machine boots from a floppy; the FDD appears in the Test menu in EZ-Setup, and tests OK.

On the good-looking machine, the same external floppy and cable, also connected to the FDD port on the back, grinds during power-up but doesn't read the disk, and the FDD is grayed out in the Test menu. The same FDD module works perfectly when plugged into the machine's bay.

This sounds to me as if something's wrong on the system board on the good-looking machine, but of course that's just a guess. At some point, I'll need to boot from an external floppy so that I can boot from the floppy and then run something from a CD-ROM, so it would be good to be able to get the external floppy to work. If I can't get it to work, then I suppose I'm in the market for a Selectabase 770 which also has an FDD port.

Does anyone have any ideas on how this problem might be fixed? I don't think I'm equal to replacing the system board, even if I had one to replace...