Re: Reducing Noise on the IIgs (Fatal System Error 0911)

[Rubywand <rubywand@swbell.net>]

"Matthew S. Carpenter" writes ...
> 
> Hello,
> 
> I recently upgraded my TWGS accelerator with a 32k cashe card.  After
> doing this My IIgs has been giving me Fatal System Error 0911 with a
> fair amount of frequency when I try rebooting the IIgs to different
> drives and sometimes when I try to go into the control panel.
> 
> After looking it up in the CSA2 FAQs I think it's likely due to noise
> problems or dropped voltages.
> <http://home.swbell.net/rubywand/Csa2HDWHACK.html#005> I have in my
> Apple ROM 01 IIgs: a LanceGS card[2], a TWGS[3], an Apple High Speed
> SCSI card[5],a superdrive card[7], and an 8MB Serius RAM card.  I've
> already done the power supply mod as explained here
> <http://home.swbell.net/rubywand/Csa2POWER.html#005> but the errors
> persist.
> 
> I was going to try adding wires to make the path from the power plug to
> the slots on the board fatter but I don't think I'd be able to do it and
> not have problems with shorting or crimping from supports in the case.
> <http://home.swbell.net/rubywand/Csa2POWER.html#006>.
> 
 ....

     One check would be to try running without the SCSI, Superdrive, and
LanceGS cards. If the 0911 errors disappear, then power problems look fairly
likely. Since you've fattened the PS leads, the PS itself would be suspect.

     If you measure the +5V voltage on the motherboard, it would be useful to
know if removing the boards makes a notable difference-- like around .25V or
more. 

     Despite the above, getting 0911 errors with any consistancy during the
keypresses you mention seems to indicate a flaw somewhere in ADB hardware.

     If your IIgs is a ROM-00 model which was upgraded to ROM-01, you may have
a borderline ADB IC-- probably the ADB GLU. Just being in a room which is
cooled during the summer could be enough to trigger a sudden rise in 0911
errors. 

     A pretty good fix for a temperature sensitive ADB IC is described in the
FAQs at http://home.swbell.net/rubywand/Csa2HDWHACK.html#005 .

     Another thing to check is the connectors at your KB. Those tend to work
loose and develop breaks between the connector and the KB circuit board. A poor
ground connection might make the ADB line more susceptible to noise.

 

Rubywand