Re: VIC-1541 problem

From: Marko Mäkelä (
Date: 2006-12-12 10:04:52

On Tue, Dec 12, 2006 at 04:15:54AM -0300, Andrew Wiskow wrote:
> I've got an issue with an old off-white VIC-1541 disk
> drive...  It doesn't play well with others, for some
> reason...  I've plugged it into a C64 and a C64c by
> itself, and it works just fine...  But plug other
> drives into the serial chain, and none of the drives
> work.  All drives are assigned different drive
> numbers.  I've also tried swapping out the serial
> cables, but it sttill doesn't work.  Has anyone heard
> of this happening before?  Any ideas how it can be
> fixed???

You could try replacing the chips connected to the serial interface.
They could be slightly damaged in such a way that they are putting
more load on the serial lines.

For more information, see the service manual
and the (slightly unreadable) schematic diagram for the long board:

I'd replace the UC1 (74LS14) and UD1 (7406).  The newer (short) board
has similar inverters near the serial bus.  I don't know of the 1541-II;
it might have these integrated in a big ASIC.


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