29 Aug
2011
29 Aug
'11
6:04 p.m.
On Mon, 29 Aug 2011 19:37:56 -0500, Tom <a50mhzham at gmail.com> wrote:
I used to sell apple ]['s and repaired them, but
seldom down to the component level. Except for
the 74LS125 on the floppy drive. Users were
always frying that by plugging the ribbon cable
backwards, something you really had to work hard to do.
Anyhow, I like the idea of checking all the caps.
True - though there are a couple of problems. I would suspect the HF
smoothing caps, situated near current sinks (rows of RAM etc). However, 1.
I've never seen one fail on an original Apple II MB, and 2. there's a bunch
of them in parallel so I can't test them individually without lifting one
leg on each, which would be annoying to have to do. Note that my memory of
how those caps are laid out on this board is very hazy, and in fact this is
the very first II Plus board I've worked on, all the others being Europlus
(virtually the same, but still). Anyway, I may end up having to do that, of
my RAM investigations are unhelpful. And I should also be able to tell
which PS rail I have to concentrate on too, which should help.
Historically speaking - I used to do the same as you in the late 80s/early
90s. I'd buy up faulty Apple IIs and clones, repair them, and sell them at
a profit to fund my bad habits when I was at school. At the time I didn't
have a very good idea of what I was doing, but it was a good learning
experience. I'd love to track down some clones again, I only have a couple
of very conventional ones at the moment. There were some great ones, like
the clone MB in an PC/XT style case (looked identical to an XT), with an
XT-lookalike keyboard as well. And the MedFly, which I think was
Australian. And there was one made by the company that eventually became
Acer too I seem to recall (what was their name back then... damn), which
was a nice-looking thing, but not 100% Apple-compatible.
Cheers,
Mike