PDP-12 Restoration at the RICM

Ethan Dicks ethan.dicks at gmail.com
Mon May 25 21:02:31 CDT 2015

On Mon, May 25, 2015 at 8:07 PM, Michael Thompson
<michael.99.thompson at gmail.com> wrote:
> Today we pulled all of the M113 flip-chips and tested them because SN7474
> and SN7400 ICs seem to be a problem in these early DEC systems.

I have found from debugging a PDP-8/i and multiple PDP-8/L systems
that 80% of my failed ICs are SN7474 and SN7440 parts, and most of the
remaining 20% are SN7400.  I think I've replaced 0-2 parts that
weren't one of those three.

Do you have any writeups on Warren's FLIP-CHIP tester?  I made a
simple rig with a 1990s-era Ming IC tester and a 16-pin clip-lead
harness that can test each chip on a simple (M113, M117...) FLIP-CHIP,
but it can't test complex boards like the M220 or M706/M707.
Fortunately, most of the failures I've run into are a small handful of
TTL on the simple single-height boards, which this rig can catch.
I've been thinking about a smarter rig but haven't tried to build one.


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