Re: How do I fix a IIgs Logic Board

[Rubywand <rubywand@swbell.net>]

MatchALot writes ...
> 
> How do I fix a logic board for the IIgs?


     Something like this ...

o- remove the power supply, pull all Slot boards (keeping notes about
which goes where and anything special about cables which may be connected)

o- remove the front mini-panel

o- undo all nuts which hold the board in place and mark these points with
whiteout. Mark and unplug the Speaker connector.

o- begin on one side of the board and free it from the plastic retainers
(squeeze and lift).

o- lift out the board.

------


     Once the motherboard is out ...

o- Clean the board: remove dust using a brush and/or blower. Clean off
grime and remaining dust using alcohol cotton swabs.

o- Pry up and firmly resocket each socketed IC. (A large needle is good
for prying up square IC's at the corners.)  Make sure each IC is plugged
in correctly.

o- Under a magnifier light ...

Look for evidence of over-heated, blown, etc. IC's and components. 

Look for anything-- like bits of wire and metal which may cause shorts
(look inside the Slots, too).

On the bottom side, look for fractured solder points-- dull, grey
looking-- and check for damaged or cut traces.

Check the battery on the board with a Voltmeter. If the Voltage is less
than 3.6V, install a new battery (3.6V, 1.2AH Lithium battery).  A
different AH rating is okay; but, if you go below 1.2AH, the battery will
need to be replaced again sooner.

------


o- This step is a bit controversial: If you are fairly sure that Radio-TV
interference will not be a problem, remove the bottom, top, and back metal
shielding from the case. Clean the case.

o- Replace the motherboard and reconnect the Speker. If the metal
shielding is gone it will be much easier to put in the board without
having to worry about shorting something. For now, leave the front
mini-panel off-- it is a pain to remove and you may want to pull the board
again.

o- Clean the power supply connector and reinstall the power supply.

------


     For testing, you want to 'keep it simple' at first. Connect a known
good monitor, 5.25" platimum drive, keyboard, and mouse.

     Hold down the OpenApple and Option keys and Power On the computer to
run the diagnostic self-test. If the machine passes, good. If not, post a
question about the error to the newsgroup.

     If the machine does not come on at all-- e.g. no ON indicator, etc.,
you probably have a damaged or poorly connected power supply. If you hear
clicking or beeping from the power supply, you may have a short on the
motherboard.
 
     If everything is okay so far, the odds are pretty good that whatever
led to checking the motherboard has either been fixed by the cleaning and
resocketing and reconnecting OR there was never a problem with the
motherboard-- i.e the keyboard, a drive, a shorted joystick, etc. may have
been the cause of problems.


     From this point on, you want to try booting a known-good ProDOS
diskette and gradually add other peripherals and try them out. (BTW, never
connect/disconnect a disk drive or plug/unplug a Slot card with the Power
ON.)  You may need to make changes in your Control Panel settings--
reached via OpenApple-Control-Esc. And, again, you can always post
questions about problems here.



Rubywand