30 Aug
2011
30 Aug
'11
3:03 p.m.
On Tue, 30 Aug 2011 20:53:12 +0100 (BST), ard at p850ug1.demon.co.uk (Tony
Duell) wrote:
Yeah, I know, I know... it's just a nostalgia thing I think! Either that or
I have a perverse appreciation of hacky solutions (to be honest, this is
actually true).
Yes. As it turned out, someone else did the KB cable for me... bah.
In the end, I found +5V was shorted directly to ground. I think that
someone has been fiddling with the machine trying to fix another fault, and
when they reassembled it, shoved the aluminium spacer that runs along the
back of the MB as far forward as it would go, causing it to touch Bad
Things. When I took the case off, I removed the spacer as well (had to to
free the rear RF shield), and... no more short. But it did leave me feeling
a bit suspicious about this machine.
> I have an Apple II mainboard I'm trying fix. I
really enjoy gettting
> these
> particular machines going, for some reason. Maybe it's that emphatic
BEEP
when they
finally run up... anyway...
Each to his pwn :-) > This one has a pretty obvious fault, it sinks too
much current on a
> yet-to-be-determined power supply line. Starting it up, the PSU goes
into
a
startup/shutdown loop. The seller said he'd tested the PS in another
OK, I
assume you know it's the mainboard (you've remvoed all expansion
boards and unplugged the kebyaord cable). My ideas so
far:
1. First thing I'll do when I get back to it is discover which PS output
is
being overloaded. That might eliminate a few suspects.
Sometimes an analogue
voltmeter will 'kick' on all PSU outputs except
one, that one is the one that's shorted.
Alternatively, pull the RAMs (the only thing that cares about multiple
supply rails IIRC) disconenct one PSU output at a time at the 6 pin
connecotr and apply a suitable dummy load to it. If you find an output
that, when disconnected, allows the PSU to come up, you know that's the
one that's overcurrenting. IIRC the ICs on an Apple ][ mainboard are all
socketed. It doesn't take
that long to pull the lot.
Yes, true. I wouldn't really mind doing this, but I really have to little
time to play with the thing, I'm hoping to avoid doing anything I don't
absolutely have to. Oh well, progress has been good.
One thing I am wondering about. The monitor I'm testing this with is a
Monitor ///. It gives a perfect picture from a Europlus (50fps), but on
this one, it looks like it can't sync to the NTSCoid output of the II+.
Might have to find something that is more 60Hz-happy. Or maybe there's
still something wrong with the video output. Will check when I next get a
moment.
Cheers,
Mike