8 Sep
2015
8 Sep
'15
9:45 a.m.
From: Holm Tiffe
Anyway, thanks for the schematics
Eh, de nada.
I have the board running again. The fix was simple,
the xtal was bad.
You're lucky it was something so simple! (Although we've seen this kind
of thing before - I had that 11/23 with a bad crystal.)
I've got three dead 11/73 boards (from someone else), but none of them are
that easy. Different symptoms on all three, but I suspect the State Sequencer
gate array on all three. On one, at least, the ILOE latch control signal from
that gate array is sitting at 2V (which I seem to recall is characteristic of
a TTL input that's not being driven).
Maybe it's just some corrosion, and re-seating the gate array (if I can work
out how to unseat it - don't have the extraction tool) will fix it.
Otherwise, I'm SOL. At least the J11 there are spares for - that gate array
is surely umobtainium.
Noel