23 Jan
2017
23 Jan
'17
1:38 p.m.
On Mon, Jan 23, 2017 at 9:23 PM, Adrian Graham
<witchy at binarydinosaurs.co.uk> wrote:
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.
Oh... The trace isn't open-circuit, is it? Check it with the
multimeter. Given the
corrosion damage to the tape drive I could well believe PCB problems of a
similar nature.
-tony
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.
Sounds reasonable...
I normally trace connections using my DMM, but of course you have to know
what will fool it (i.e. low resistance components). I find I have to desolder
relays, switches, inductors, transformers, low value resistors, etc before
starting to trace the circuit.
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?