From: Ray Bryan (raycomp_at_visi.com)
Date: 2002-04-09 00:22:22
On Mon, Apr 8, 2002, at 09:43 PM, Daniele Gratteri wrote:
> Hello,
> from few weeks, I have got a VC-1541, the cream 1541, which has the long
> logic board. Well, I tried it on my "new" C64 C and found that it doesn't
> work: it turns on, ok, but when I try to access the drive, with ANY
> command,
> the drive doesn't reply and the red LED doesn't flash any time.
> I tried its ICs (the 6502, the two 6522s, the ROMs) on my good 1541 and
> found they work. I also connected the mechanism to the good 1541 and it
> also
> works fine.
> Do you know what can be the damaged IC? Surely it is one of these many
> TTL...
>
The long logic board had all discrete logic instead of the large logic array of
those later boards, but this sounds like 7406 or 74ls14 on the serial line in has
failed (a common occurence). The same thing happens on the shorter boards.
On that board they are labeled UD1 & UC1 - check the pins with a scope or
logic probe. on UD1 the pins are paired as - 1-2,3-4,5-6, 9-8, 13-12,
the out pin should always negate the input - if input changes and output does not
or output=input bad gate
--Ray
--
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|Raymond C. Bryan 651-642-9890 vox | The battle is sometimes |
|Raymond Computer 651-642-9891 fax | to the small for |
|795 Raymond Ave -email: raycomp | the bigger they are |
|St Paul MN 55114 @visi.com | the harder they fall. |
|USA Amiga - Commodore | -- James Thurber -- |
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