Date : Fri, 24 Feb 2012 13:51:26 +0000
From : bbc@... (Dave Curran)
Subject: Acorn Electron Repair - Replace 6502 (unlikely)
Unfortunately, the chip was damaged as it was removed - I was concentrating
on not damaging the board. On the plus side, I've probably saved myself a
couple of days analysing why it failed. Not sure if I'd be able to get as
for as you did, but it is sometimes interesting following these things up.
I'd be interested to know how it died, if the cover on the expansion slot
had been missing, I'd blame static, I suppose it's still a possibility if
you slide it along the wrong type of carpet and get a spark. Most of the
connector is wired direct to the CPU.
Time to get onto ebay and find a cheap 6502, or I may see if I can get one
of those new ones? It should work in an Electron.....
Thanks,
Dave
On 24 February 2012 11:19, Rick Murray <rick@...> wrote:
> Hi,
>
> Once came across a Beeb that had a broken CPU in that the maths ops seemed
> to be stuck in BCD mode irrespective of the flag setting. Beeb, naturally,
> failed to start, so at school we cobbled together a test rig on veroboard
> to be controlled by another Beeb's printer/user ports. Many weeks of assing
> around (like you do) and the penny dropped for one of the more mathsy
> types. So a dead-simple boot was written to power up taking account of the
> BCD maths, and it worked to spit out a square wave on one of its address
> lines. Dunno how or why it would fail in this way, it just did.
>
> If you have time and enjoy experimenting, you could poke around the "dead"
> processor. Or... not. :-)
>
>
> Best wishes,
>
> Rick.
>
> Dave Curran <bbc@...> wrote:
>
> >I've been working on an Electron I picked up at a local flea market.
> >'untested' as usual means broken. Blank screen, no signs of life.
> >
> >After going through all the usual tests, it's turned out to be the 6502
> >which had gone. The service manual lists this as 'unlikely', is that still
> >the case? I can't remember having this on any of my B's or Electrons, but
> I
> >suppose half a century later it may be more common?
> >
> >Full story and photos on my blog:
> >
> >http://tynemouthsoftware.blogspot.com/2012/02/acorn-electron-repair.html
> >
> >Thanks,
> >
> >Dave
> >
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