RE: Problems with a long board 1541

From: Ray Bryan (
Date: 2002-04-09 00:22:22

  • Next message: Spiro Trikaliotis: "Re: Problems with a long board 1541"
    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 
    |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     | the harder they fall.   |
    |USA              Amiga - Commodore |     -- James Thurber -- |
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