10 Dec
2002
10 Dec
'02
10:36 a.m.
Hi Phil
If you know a part is bad and you want to remove it
from the bard with the least damage, clip the leads
close to the part and then remove the leads, individually,
with a pair of tweezers/iron. Always use a temperature
controlled iron set to the point that a clean tip
will melt the solder of the joint in about 10 to 15 seconds.
Even really cheap PC board can be reworked if one
uses some care in methods. I don't recommend using solder
wick. Many do well with it but it tends to get stuck
to traces if not overly heated and will lift traces.
If you use a solder sucker, don't use a small one.
Use one with as big a bore and stroke as you can find.
Dwight
From: "Philip Pemberton"
<philpem(a)dsl.pipex.com>
Hi all,
Well, it looks like I've finally destroyed the Ace. I've just spent the
past hour trying to desolder the dead RAMs and buffers from the Ace's main
PCB. Unfortunately it looks like the board was designed to self-destruct
when anyone tried to repair it.
The pads appear to have been designed to peel off on the application of
heat, they're less than 5 mils around the hole (what do you think that
means?) and they don't even seem to be through-hole plated. The tin plating
was applied straight on top of oxidised copper - I've had to retin some
pads
and tracks courtesy of that major screwup.
In my opinion, the Jupiter Ace is one of the most appallingly-made
machines I've ever tried to repair. Heck, the Commodore 64 was bad, but at
least the pads were easy enough to desolder. It looks to me like Jupiter
Cantab's PCB designer was either *VERY* inexperienced or just wanted to
make
sure that no-one could fix an Ace if it failed.
It's also beginning to look
like the ROMs are stuffed, but that shouldn't be too hard to sort out --
I've just bid on some 2532 EPROMs on eBay from someone in Austria.
Does anyone know how I could rescue this machine? It looks like the
RAMs
are definetly fried, along with some of the logic as
well. Font RAM and
Video RAM are still not being loaded on startup so the output of the video
generator is still 100% noise, however it *is* changing when the machine is
powered off and then back on again. I'm shotgunning all the RAMs (there's
only six of them) and the bus muxes.
Has anyone here either repaired one of these machines or got a spare
Ace
to sell me? I've got a proper PSU now, with only
one connector (the jack
plug the Ace uses), so I can say with near absolute certainty that the same
mistake will not occur again.
Later.
--
Phil.
philpem(a)dsl.pipex.com
http://www.philpem.dsl.pipex.com/