On Wed, Jan 4, 2012 at 3:14 AM, Holm Tiffe <holm at freibergnet.de> wrote:
Like it too.
I've repaired several old computers (no PDP8) and it is always fascinating
to read such blogs. I know "mass dead effects" of several TTL chips too
Don't know if it's similar to what you've seen or not, but from my
experience testing M-series modules for the -8/L and -8/i, I've found
more dead 7474s and 7440s than any other type of chip.
For my testing, I rigged up a 3M test clip
(
http://parts.digikey.com/1/parts/389650-16-pin-test-clip-3-row-space-923700…)
to a ribbon cable with two IDC headers crimped on one end about an
inch apart so that I could mount one IDC connector on each side of the
clip, then cobbled up an adapter for the other end of the cable from a
wire-wrap socket so that in the end, I had a cable that could clip
onto one IC and fit into the ZIF socket of a hand-held IC tester. I
would test my FLIP-CHIP modules out of the box, letting the tester
power all the ICs on the board but only fiddle the lines on the chip
under test.
With that device, I could test a pile of M111, M113... M216, etc.,
boards in a few minutes and identify failed ICs. Complex boards like
the M220 Major Registers module, though, still have to be tested the
hard way.
-ethan