29 Jan
2012
29 Jan
'12
7:59 p.m.
As if I needed another project, I picked up a 1581 yesterday at SRCS in
unknown condition. Hopefully this won't distract me from my Cromemco
floppy issues for too long :).
The power switch was broken (permanently stuck in the "off" position) so
I replaced it with one from a "parts" C-64. Once that was repaired the
symptoms I'm seeing are:
- Both LEDs on the front come on and stay on permanently. My
understanding is that the access light should turn off after about two
seconds.
- If the drive is hooked up to my C128 at powerup, the 128 will hang
after displaying the startup banner (I assume it's waiting for a
response from the drive and not getting one...)
- If a disk is in the drive, the disk will spin for a second or so and
the heads will seek back to track zero.
The last item makes it seem like the 6502 is running and that the EPROM
contents are still valid. I dumped the EPROM and verified that its
contents are correct against an image from the 'net. The power supply
is a known-good & tested supply I've been using with a 1541-II. 5V and
12V supplies look fine. For good measure I've cleaned the sockets &
pins for the EPROM and the WD1772 (the only two socketed chips).
Anyone have any tips for narrowing down the fault before I start digging
through the source listings & schematics?
Thanks as always,
Josh