23 Jan
2017
23 Jan
'17
1:23 p.m.
On 23/01/2017 19:07, "Tony Duell" <ard.p850ug1 at gmail.com> wrote:
Yes, just found it after some leg cleaning. This board is a big fan of
running small traces under other components. Looks like it's a 68pF ceramic
type.
I've been looking for shorts but I'd have thought that anything that's A7
should go high at the same time as long as it's part of the same trace, so
the LS373 to MC3242A to pin 3 on all four ROMs should pulse together and
they don't. If there's a short they should all get it.
Since this is an 8085A powered machine it runs internally at 3MHz so I
should be able to sample it at over 12MS/s. Another collector friend is
loaning me an analyser that can be externally clocked but it's still USB
connected like both of mine are. I'm pondering an HP/Agilent 1663A that's on
ebay for 'offers'...
--
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
collection?
I didn't
think of a 555 in that scenario but that makes sense. I've marked
it as such for now, cheers!
Is there another capacitor from the 2/6 junction to chassis? Any other
components
around? It might be one of the special SMPSU ICs, but it doesn't
instantly ring a
bell with me. Tonight
it's 'address pins and why I get inconsistent results on a logic
analyser while looking at everything that touches A7' :)
Short from A7 to another pin? Failed address latch?