M220B (PDP-8/I) schematics available

From: Tothwolf <tothwolf_at_concentric.net>
Date: Thu Jul 10 15:20:01 2003

On Thu, 10 Jul 2003, Tony Duell wrote:

> > This reminds me of a similar problem in the JC80 systems, where 74170
> > chips would fail more often than anything else. I'd sure like to know
> > what the cause of that was...
>
> I can remember replacing many 7474s in the RK11-C when I was getting
> that going. Oh, and a 7482 adder, which was impossible to find [1]...
>
> [1] I do mean _impossible_. I ended up using part of a 7483 that I stuck
> to the flip-chip PCB dead-bug style and wired to the holes where the
> 7482 should have been. Runs fine...

You know what happens when someone says impossible...

I just checked my parts bins, and I have *one* 7482, a TI part with a date
code of 7541. If you still want to replace your 7483 kludge, and know of
an economical way to get small things from the US to the UK, let me know.

Btw, what was the vintage of the old chip? Chances are one of the local
surplus places I visit from time to time has some 7482 chips in one of
their bins.

-Toth
Received on Thu Jul 10 2003 - 15:20:01 BST