1 Sep
2011
1 Sep
'11
2:31 p.m.
On Thu, 01 Sep 2011 19:23:18 +0100, Pete Turnbull
<pete at dunnington.plus.com>
wrote:
This is the value I remember from many years ago when I used to mess about
with these machines. It would explain why the crystal was floating in the
air rather than glued to the board as it normally is. Looking carefully, it
looks like someone has had a fiddle with a few of the frequency settings.
The 50/60Hz pads have been changed from default, too. I expect this machine
was imported into NZ (probably from the US) when it was relatively new, and
someone's converted it to the local frame rate. Seems strange when most
monitors would have worked with it as it was.
Pondering... if this machine has 50/60Hz pads to switch it over, why would
anyone need to replace the crystal? It seems a bit odd.
Anyway, I'm strongly tempted to return it to its default configuration,
though I'm sure it'll work fine set up the way it is. At least I have a
choice; if I can't find a 14.25045MHz crystal, 14.318 would probably work
fine.
Cheers,
Mike
I doubt this is the cause, but I once had a similar
effect with a BBC
Micro and a Torch disk pack PSU. The Torch processor, mounted upside
down inside the lid of the BBC Micro, fell off and shorted something on
the main PCB below. The PSU apparently shut down, but had a serious
voltage overshoot when it started up again, and put about 8V or more
onto the 5V rail. That took out quite a few LSTTL chips. Oh, and the
way we found out which ones was to put a big bench 5V PSU on the machine
and see what got hot because it was drawing too much current...
It is possible I guess. I might have to work on the assumption that a good
number of the ICs on this board are dead. Fortunately, most of them still
seem to be easily available. And besides, I like working on these things,
right? I should be happy that my enjoyment will be stretched out a
little...
I should try to figure out exactly how the video encoder works in these
things. I hear the design is a bit... creative. Maybe there's a decent
description on the web somewhere.
> Silly question of the day: I'm guessing no-one
would have any idea where
I'd find a
14.25045MHz crystal in New Zealand...
No, but the standard crystal in an Apple ][
is a 14.318MHz crystal, and
that's a standard so should be very easy to find. I wonder if yours is
a special value for a non-US market? But AFAIR even the Apple Europlus
used 14.318MHz.