Re: IIgs Rom1 _weirdness_

[rubywand@aol.com]

In article <5cr8u8$1ae$1@portal.mbnet.mb.ca>, tmyers@autobahn.mb.ca (Todd
Myers) writes:

>.... I also get $0911 errors
>after it's been on for about 30 min., the HD is on top of the GS box
>and it has a fan on the bottom for air flow thru the GS.
>
>I tried to fire it up about 4 months ago using a IIc monitor, but got
>$0911 errors at powerup...I could not even bring up the text Control
>Panel.
>
>The GS has the IIe keyboard jacks on the motherboard, so it could be
>a Rom0 that was upgraded (or partially upgraded). I need a little help
>with this. I have more cards in it now so it could still be a flakey 
>power supply. But I think it's a blown-gate on one of the MB chips
>(cpu?), or a cold solder joint somewhere. The weird thing about this
>is that I can only boot from 800k volumes...nothing larger. ....


     It is likely that, if your ROM-01 GS has a ROM-00 board which was
upgraded, then, it got the new ROM plus the Video chip. The full upgrade
was, after all, free.

     The 0911 error is, almost certainly, related to a defective ADB
Controller IC. This is a fairly common problem on early GS motherboards.
It does, also, help explain why so many ROM-00 and "ROM-01" machines are
available at bargain prices.

     While you may have other problems, a good start is to eliminate those
which may result from a flaky ADB IC. In this regard, you face a classic
Bad News/Good News situation.

     Bad News: The ADB IC is soldered in place; and, in any case, about
the only source for a guaranteed good ADB IC is another GS motherboard
known to have no ADB bomb problems.

     Good News: There is a fix which may nearly eliminate ADB glitching.

     The fix was first published in Computist many years ago:


ADB IC 0911 Fix

     Tape a small 12V panel light bulb to the ADB IC with duct tape
enclosing the bulb and IC to form a mini-oven. The bulb is powered using
the 12V fan power pins located near the left back of the motherboard.


     The idea is that, since we are dealing with malfunctioning over a
range of
relatively low temperatures, it is a good idea to help warm up the IC as
quickly as
possible to get it past the glitch range of temperatures and keep it
there. This fix nearly eliminated 0911 bombs on our Woz edition
motherboard. (Like, they went from a few each day to one every few weeks!)

     If the bulb were powered from a separate 12V plug-in transformer
(e.g. one designed to be plugged in all the time for running a radio,
etc.), the temperature would never drop into the 'glitch range'. This
might eliminate ADB IC-related crashes entirely. 
 

     Regarding other possible problems ...

     Having the HD sitting on top of the GS may lead to problems. Unless
your HD case is designed to supply cooling to the GS, you may have too
much heat coming into the HD.

     You GS does not seem to be overloaded vis-a-vis the standard Power
Supply's capacity. It is, possibly, overloaded with respect to the
standard PS's skimpy leads. These act like resistors which drop voltage
and increase system noise. The +5 lead and one Ground lead should be
replaced with #12 (stranded) wire leads. The +12 lead should be replaced
with #14 wire.
   

Rubywand