Dragon 64 fixing...

From: Jules Richardson <julesrichardsonuk_at_yahoo.co.uk>
Date: Tue Jul 20 06:15:14 2004

On Tue, 2004-07-20 at 10:40, Philip Pemberton wrote:
> In message <1090317397.28481.21.camel_at_weka.localdomain>
> Jules Richardson <julesrichardsonuk_at_yahoo.co.uk> wrote:
>
> > Of course, it's
> > likely to be something simpler I expect...
> Get an oscilloscope and a logic probe out then :)

:-)
It's looking that way...

Power's getting where it should be and the reset's ok; I haven't checked
clocks for anything yet though.

One thing I have found though - a *lot* of chips in this machine are
replacements, and the solder quality is total crud.

All the RAM chips and both MC6821's are replacements, and the sockets
for the LM1889 and MC6847 look to be non-original too, implying that
those suffered some form of destruction and were replaced. Given solder
quality, I'm going to check continuity on the address / data lines for
all the RAM chips and check for shorted tracks too.

I've already disturbed something and now the machine powers up and gives
a black border / green screen with no garbage - I just don't get any
text display either, so it's still not happy.

For some reason one of the RAM chips has a 220n decoupling cap, whilst
the rest are 100n.

Be nice to get it working as this is a grey-cased machine with GEC
labelling, plus I have the box and a boxed floppy drive to go with it...

cheers

Jules
Received on Tue Jul 20 2004 - 06:15:14 BST