One more screwup with the Ace...

From: J.C.Wren <>
Date: Tue Dec 10 14:16:01 2002


        Most likely the board was designed for low cost. If there is no
soldermask, larger annular rings increase the chance of solder bridges
during manufacturing. But more likely, smaller annular rings were used to
reduce the amount of solder needed, thus lowering the cost. I don't believe
they Ace nor the ZX81 nor any of that genre of computers was designed to be
repaired. They were designed to be produced as cheaply as possible.


-----Original Message-----
From: []On
Behalf Of Philip Pemberton
Sent: Tuesday, December 10, 2002 15:04
Subject: One more screwup with the Ace...

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.

Received on Tue Dec 10 2002 - 14:16:01 GMT

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