Date   : Wed, 01 Nov 2006 21:58:28 +0000
From   : astravan@... (Alex Taylor)
Subject: Dead Beebs

Hi

After improving some of my dodgy CUB monitors, I'm now trying to sort 
out dead Beebs. All the ones I bought from Wales turned out to be faulty 
in some way, except maybe the Master ET which I haven't even turned on 
yet. I have a load in bits and I'm starting to forget what's wrong with 
them all.

I have three or four that just emit the initial startup tone but don't 
get to the beep. I'm sure I've seen a fault-finding guide for this but 
can't find anything - does anyone have any pointers?

I did have one with a hardware scrolling fault. I was going to change 
ICs 32 and 39 but I think I've killed this one in the process (see above 
about the startup tone thing).

I've got one that crashes with a corrupt screen if it's been on for a 
while. I've swapped the Video ULA and the 6502 with no difference, and 
nothing seems to be excessively hot. Could this be bad RAM, and how do I 
find which chip is bad?

I think that's all of them accounted for. I have the service manual and 
circuit diagram, but I'm not really an electronics person. I'd 
particularly like any advice about the ones that don't get past the 
startup tone.

Thanks


Alex Taylor