Liam Proven <lproven at gmail.com> writes:
[...] the donations chap at TNMOC has put The Fear
into me by sternly
warning me Not To Turn Any Of Them On, because They Will Blow Up.
That's a bit over-the-top. But more or less accurate. ;-)
The explosion in question is the result of the power supply's mains
filter capacitors suffering from perished plastic after 30-odd years. If
you run an old BBC for a while without replacing them, you'll eventually
get a quiet "pop" and a cloud of evil-smelling smoke. The machine will
actually continue to work just fine, but the EMC performance is
presumably somewhat degraded, and you'll want to scrape all the bits of
exploded capacitor out to get rid of the smell.
Sprow's BBC repair FAQ has a section on replacing these, which is quite
straightforward -- it's awkward enough to get into the power supply that
you may as well replace the other parts he suggests (all available from
CPC or a similar electronics supplier) at the same time:
http://www.sprow.co.uk/bbc/howto.htm#powersupply
Note that the same power supply board is used in some BBC Micro disk
drives; I've got a Watford dual drive which had exactly the same
problem.
Other than that, I've found BBCs to be extremely reliable; I've cleaned
up several for friends over the last few years and only found one that
didn't boot first time (because somebody had stolen the disk controller
chip and not adjusted the jumpers to suit).
Don't forget to check your machines to see if they've got any
interesting sideways ROMs in!
Thanks,
--
Adam Sampson <ats at offog.org> <http://offog.org/>