Yes indeed. Well solder joints get dry due to oxide forming on the component
wires where the solder did not take correctly to start with.

The effect used to hit pcbs before plated through holes where rivets used to
do that job and of course under a high powered magnifier you could see the
furryness forcing its way under the solder.
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. OK 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.
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. In the old sets the afc followed the drift, but not the newer
models. Often, its better to wire up a monitor lead and get the sound out as
audio.
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. You
can get new ones fairly cheaply of course.
Brian

--
Brian Gaff -
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"D.M. Procida" wrote in
message
...
My Christmas present to the children was a Commodore 64.

I picked it up a couple of months ago, and ran it for several hours to
test it; it was all fine.

On Christmas Eve I tested it again; after a few minutes it would start
throwing junk all over the display and then lock up, and I realised that
the difference was the house at room temperature where it crashed, and
the much cooler garage where it wouldn't.

We've repaired it now (mostly), by resoldering many of the pins on the
PCB where the solder seemed to have developed holes. I've never noticed
this phenomenon before, even in much older equipment. I assume that it
wasn't like that after manufacture.

What causes it?

Presumably, a 30-year-old computer would have had proper lead solder,
not this tin-whiskery lead-free stuff.

Actually it can't have been the soldering alone that fixed it because it
continued to crash; I also used a hot air gun to try to identify the
component that was failing after warming - I only once managed to get
that to trigger the fault, but since then, it hasn't crashed again.

So the crashing is fixed, but the next thing to tackle is the sound
output, which is barely audible.

Anyway, the children have been happily playing The Hobbit and Attack of
the Mutant Camels from tapes that have been sitting in boxes for nearly
three decades, which isn't bad going.

Daniele