II+ flakiness

[Linards Ticmanis <ticmanis@gmx.de>]

Hello all,

during the last maybe 6 or 9 months in storage, my II+ seems to have
developed an odd but annoying fault: Now it has the habit of crashing
roughly every 30 to 60 minutes. RAM seems to suddenly fill with $FF for
some reason (the screen will either fill with question marks "?" or go
white, depending on whether it's in text or graphics mode), and then of
course the computer goes dead. "Reset" will revive it.

The problem seems (note, *seems*) not to occur if the computer is just
sitting at the BASIC prompt, but it does occur with different programs
running - such as FID from DOS 3.3 (sitting at its prompt) and several
games.

Any idea which chip might cause this? I tried removing all cards except
for the disk II controller (but I exchanged that for another one), and
it didn't help. Neither did pressing down on all the chips. Running with
the case open didn't seem to make any difference either, and no chips
seemed to get particularly hot. The ROM chips were warmish, but I tried
putting in a set of Integer BASIC ROMs instead, and it didn't change the
crashing behavior. I'm currently running the continuous memory test from
the Programmer's Aid #1, but it doesn't seem to find any problems.

Thanks,

-- 
Linards Ticmanis