User`s guide

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From: Rubywand, David Kopper, Guenther Unger, Gabriel Hawkins, Michael Mahon
005- I've been getting Fatal System Error 0911 and when I
do the internal diagnostic it gives a system bad :
09010001. Is there a fix?
Fatal System Error 0911 and Self-Diagnostic Test 09010001 mean the same
thing: You are, very likely, experiencing one of the following malfunctions:
o- Temperature-sensitive ADB IC
This problem was first identified in a 1988 article in issue #58 of
Computist. If your IIgs is a true ROM-01 (produced starting in mid-late 1987) or
a ROM 3, you are very unlikely to have an ADB IC with this defect.
Otherwise ... A guess would be that you are running a ROM-00 machine which
has been upgraded to ROM-01. If this is the first time you've noticed the '0911
problem, it is likely that this is the first summer you've owned and used this
particular machine.
Many early GS's come with an ADB IC which malfunctions over a narrow range
of relatively low temperatures. Rooms are normally cooler during summer; so,
this is when the error pops up most frequently. Some users first notice a plague
of '0911 crashes after adding a System Saver-GS (which increases cooling).
Note: Some reports have attributed '0911 crashes to overheating of one of the
two main ADB IC's. So far, it looks like these reports are cases of
misinterpreting the actual failure syndrome-- i.e. warming up a cool IC enough
to get into its failure region.
'0911 bombs can occur 'any time' but they usually happen at startup and when
doing OpenApple-CTRL-ESC accesses to the Desk Accessories (CDA's, Control Panel,
...) menu. As the machine warms up, '0911 crashes tend to become less likely.
The bad news is that there is no 100% fix except to replace the temp
sensitive ADB IC-- hard to do since it is soldered to the motherboard and, in
any case, known-good replacements are difficult to find.
As to _which_ ADB IC-- there are two, the ADB Controller and the ADB GLU- -
our notes say the ADB Controller; but, we could have easily misidentified the
function back then and the ADB GLU IC 'clicks' better with memories of the fix.
(The ADB GLU IC is a square IC near the right front of the motherboard.)
Note: The easiest way to identify the temp sensitive IC is to apply the fix
(below) and see if it works. If it does, fine. If not, it is easy to move the
fix to the other IC. For now, my suggestion is to try the ADB GLU IC first.
Since the problem is coolness, a decent cure is to tape a small 12V bulb
(e.g. a 20-30 ma. panel light bulb) to the top of the ADB IC. Use duct tape and
try to enclose the bulb and IC in a kind of mini-oven. Run the leads from the
bulb to the +12V Fan power pins near the back left area of the motherboard.