Transformer part ID please

Tony Duell ard.p850ug1 at
Mon Jan 23 15:38:24 CST 2017

On Mon, Jan 23, 2017 at 9:23 PM, Adrian Graham
<witchy at> wrote:
> On 23/01/2017 19:07, "Tony Duell" <ard.p850ug1 at> wrote:
>>> 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.
> 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.

>>> 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?
> 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.


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