10 Dec
2002
10 Dec
'02
3:22 p.m.
On Dec 10, 20:03, Philip Pemberton wrote:
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.
Machines like that were designed to keep the cost as low as possible, and
repairability often wasn't a consideration.
On things like that, I often don't even try to rescue any suspect ICs or
even passives, just cut them off close to the PCB with a very fine pair of
sidecutters, and then desolder the stub of pin.
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.
First thing is to make sure anything you remove is replaced with a good
quality socket, and if necessary that you can repair any damaged tracks
with stripped wirewrap wire or similar. How adept are you with a
soldering iron? I used to do this sort of thing for a living, and I'm not
too far away if you want someone to take a look at it.
Did you get the 2114s and Z80 I sent you? They should have arrived this
morning.
--
Pete Peter Turnbull
Network Manager
University of York