From: Ray Bryan (raycomp_at_visi.com)
Date: 2002-04-09 21:08:20
On Tue, Apr 9, 2002, at 07:14 PM, Daniele Gratteri wrote:
> > 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
>
> This is an interesting thing: I cheched UC1 and UD1 and found that,
> probably, they had already been substituted in the past since solderings
> are
> different from the other ones. But, damn, they haven't installed sockets!
> :-(
> I have desoldered both UC1 and UD1 and I will put in new parts as soon as
> possible (at the moment I only have a 7414: could it work, also if it isn't
> an
> LS?). Can you confirm that UC1 is the '14 and UD1 is the '06?
Danielle,
I have the Schematic for 1540008 (board) layout 1540001 in front of me - parts list
says uc1= 74LS14; ud1= 7406 this list _does_not_ suggest 7414 as a substitute
(does not mean it won't work -just not recommended - speed might be critical).
I forgot to note that the long board 1540001 also uses 4 2114 memory chips instead
of the the single TMM2016/m58275 for the 2K of RAM.
--RAy
--
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