Apple II Computer Info
down.
Associated side-effects: flashing and/or inconsistent
brightness fluctuation while trying to adjust the external
brightness and contrast controls.
PROBLEM: Primarily in the high voltage transformer. This
'fires' the electron guns, which produce the raster. This
is adjustable up to a point. The side-effects are dirty
controls; they can be cleaned.
THE FIX: The easy one first -- even if it's not necessary,
you might as well do it while you're in there. Clean the
brightness and contrast controls.
DISCONNECT THE MONITOR FROM THE COMPUTER AND FROM THE WALL.
For safety's sake, I suggest doing this a day or two before
working on it.
Open the GS monitor by removing the four screws, two on the
back of the top 'flange' around the screen, two on the
bottom facing the front, in the long 'channels'. Slide the
back off of the monitor slowly, until the edge of the back
is even with the back edge of the motherboard, the circuit
board on the bottom of the monitor. Feed the power cord
through the hole in the back as you slide it off. The wires
leading to the controls on the side of the monitor might
hang up. If so, simply loosen them and continue. Once the
back is free of the chassis, slowly slide the back towards
the right side (as you face the front) of the monitor. This
is so you don't put strain on the wires going to the
controls on the side.
Look inside the back, at the controls. The power switch,
brightness and contrast controls are all mounted on the
inside of the back. You can clean the brightness and
contrast controls, to alleviate the flashing or inconsistent
response. Using a pencil, mark the controls and the case
so that you can set the controls back where they were before
you started messing with them.
Get a spray can of NON-ABRASIVE contact cleaner. (This is
probably al you'll find; the abrasive type was mostly for
the old mechanical channel changer-tuners, but make sure).
Make sure it won't hurt plastic. It will say so on the can.
Try to get a can with a straw that fits into the spray cap.
Spray some into one of the two controls, and turn it up and
down repeatedly. Do this a few times. Then do the other
control. Allow these to dry completely before you try to
fire up the CRT. If this doesn't fix this problem, it's
likely these will need to be replaced. The parts look to
be fairly common. Sorry, I don't have details on them, so
you'll have to get help with this.
Now to attack the main problem.
Look at the body of the CRT (picture tube). There's a big
fat red (usually) wire coming out of it to the right of the
long 'neck' of the tube (looking from the rear now). This is
Apple II Computer Technical Information : Apple II Family Hardware Info
ftp://ground.ecn.uiowa.edu/2/apple2/miscinfo/hardware : May 2001 : 298 of 572
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