Apple II Computer Info
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### FILE : monitor.repair
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### Created : Friday, September 27, 1996 Modified: Friday, September 27, 1996
### File Type: "TEXT" File Creator: "LMAN"
### File Size: 4577 bytes 4 KB
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Subject: Re: Repair Apple IIGS RGB, info wanted
Date: 21 Mar 1996 14:56:34 -0500
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Monitor Repair Mini-Manual (mostly from stuff in COMPUTIST)
First, be safe. (See safety stuff at end.) Mainly, unplug the monitor
and let sit for a day, wear goggles, work on non-conductive table surface,
do not stress CRT neck.
Whatever it is you plan to fix, if you remove the monitor case, you
will probably need to unplug the cable running from the circuit board to
the Controls/Switch Module on the side of the case. Use 'whiteout', nail
polish, etc. to mark the position of the plug.
If the monitor exhibits major flickering, periodic collapse of the
display to a line, etc., then it may help to know that a common source of
such problems is one or more bad connections where the High Voltage module
is joined to the main circuit board. (This module is the black thing with
a HV lead running to the CRT-- it's near the left, back. The slotted nub
controls in its case set Focus and base Intensity.) Often these
connections look okay because it is hard to see the small fractures in the
solder surrounding the pins.
The cure is to resolder all of the pins coming from the module (on the
under-side of the circuit board). Before doing the soldering, clip a wire
to the metal chassis and touch the other end to each HV module pin and
other points in the area. While soldering, avoid touching anything
conductive on the monitor with anything but the iron and solder.
All-blue, all-red, etc. screen? You probably have a blown choke on the
little chroma board mounted to the back of the CRT. The choke will be
connected to one of the larger, R/G/B output transistors. Use an Ohmmeter
to find the open choke. Replace the bad choke with 'one like it' or brew
your own: wind about 25-30 turns of #30 wire on a small ferrite core.
For all soldering use a good quality pencil-style iron rated at 25-40
watts with a holder. Use high quality (60/40 or better) rosin core solder
Apple II Computer Technical Information : Apple II Family Hardware Info
ftp://ground.ecn.uiowa.edu/2/apple2/miscinfo/hardware : May 2001 : 295 of 572
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