Jules Richardson wrote:
On Wed, 28 Dec 2011 09:27:55 +0000, Brian Gaff wrote:
Another thing I encountered recently via a sighted person was that some
of
the chips of that era had poorly plated pins and in some cases they
actually oxidised completely through causing all sorts of problems.

Yes, I've seen that too, particularly on 1970s and very early 1980's
machines. In some cases they seem to rot from the inside-out, so visually
the pins look OK but electrically and mechanically they're very weak (I
remember needing to replace about half the ICs in one particular machine)

if its a z80 or 6502 etc, processor there are still some made but some
of the custom chips like in the 64 you are stuffed.

I've fixed a few Commodore PETs over the years, but didn't mess with the
C64 so much - although I remember working on SX64s (which IIRC are much
the same guts) and there was one particular custom IC which had a
reputation for failing for no good reason.

With regard to sound. Are you using a modern analogue tv to get the
sound out?
Most of these are digitally tuned and the modulators in these computers
tend to drift.

Picture, too; my ZX80 was a right ******* when it came to getting any
form of remotely modern TV to lock on to its signal.

some of these older machines have psu faults. The ripples on the
picture or
hum on sound make it rather obvious that the capacitors have dried out.

In some cases, yes. The vast majority of faults I've found to be
mechanical in nature - keyboard switches, connectors, IC sockets etc.

Occasionally a reset circuit will die, and memory faults are reasonably
common.

I've lost count of how many times I've seen one of the noise surpession
capacitors on the mains side of a PSU let go with clouds of smoke,
though.

cheers

Jules
Isn't it better to get one of those emulator things and run the games
under that?

a pentium running a Z80 simulator is still faster than a z-80 :-)