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Many owners of the Apple 15" Multiscan monitor have experienced
problems with sudden and/or erratic changes in the monitor's
colorimetry.  The most common manifestation of this problem is the loss
of the red component, leaving the display blue/green.  Others have
experienced a totally red screen, as well as other odd hues. 
Generally, this problem will at first be intermittent, then will
gradually worsen to a 'permanent' state, although sudden permanent
failures are not uncommon.

When my first 15" display went blue, I decided to investigate the
problem myself (being an ardent tinkerer), before allowing myself to
fall prey to the repair industry.  I found, after some poking around,
that the fix was very simple, and have since successfully repaired
dozens of 15" monitors using my slightly unorthodox technique.

In every case I have encountered, the problem has been a loose
connection somewhere on the color board, a 4x5"-ish printed circuit
board attached to the back of the picture tube.  I say somewhere
because it's not always the same connection causing the problem.  These
loose connections were typically the result of a poor soldering job by
the factory.  In some cases there was no solder at all on the errant
connection!  Others would have a very small amount of solder that might
have broken loose from the circuit board from ordinary thermal
expansion/contraction during operation.

My repair procedure consists of the following steps:

1.  Disassembling the monitor.
2.  Locating the problem.
3.  The fix.
4.  Reassembly.

A word of caution:  There is plenty of harmful electricity to be found
in any monitor, especially if it is plugged in, even more especially if
it's turned on.  We're going to do BOTH, so be careful not to touch any
components inside with your bare hands.  Of particular concern is the
ion trap (the big wire coming out of the side of the picture tube) and
the transformer to which it is attached.  As much as 20,000 volts can
be found in this area!  There are also a couple of capacitors nearby
that carry considerable voltage even when the unit is unplugged. 
Enough said for now.

Tools needed:  You'll need a Phillips screwdriver, something
non-conductive you can poke around with (a chopstick works well), a
soldering pencil with a reasonably fine point, a de-soldering syringe
(Radio Shack - $2), a small piece of rosin core solder, and something
to release the 2 catches on top of the monitor that hold the back on (I
use an Allen wrench just small enough to fit in the holes).  Also, if
you can't see up close anymore, like me, you'll need your reading
glasses and/or a magnifying glass.


Disassembly:  Turn unit upside down & remove the swivel base by lifting
the locking tab and sliding the base rearward.  Remove the two Phillips
screws on either side of where the swivel base was.  Place unit face
down (screen down).  Use a towel underneath to keep from scratching the
screen.  Using an Allen wrench, ice pick, nail, or anything you can get
in the little square holes behind the top of the bezel (insert about
1"), pry gently outward from the monitor to release the plastic
catches.  This can be a little tricky if you've never done it before. 
I usually do one at a time while keeping rearward pressure on the back
half of the cabinet.  Once you've got them free, lift the back of the
cabinet up a few inches, enough so you can reach in and disconnect the
small speaker wire connector from the amplifier circuit board.  This is
easy to spot because it prevents you from fully removing the back.  If
you jerked the back off before you read the last sentence, you're
probably still okay because the connector faces in such a way as it
will pull out without breaking.  Remember where that audio connector is
for reassembly (small board on the side).  Holding the sides of the
bezel, you can ease the monitor back down to rest on its bottom.  A
magazine or newspaper underneath will keep it from scratching your
dining room table,  You are using your dining room table, aren't you? 
Now, the area we want to investigate, the color board on the rear of
the picture tube, is enshrouded by a shiny metal shield box.  This
shield is soldered onto the board and must be removed.  Using your
desoldering syringe, heat up and desolder the 5 attaching points. 
Nothing particularly delicate of heat sensitive here, although you
don't want to put too much strain on the picture tube connector.  Once
the attachments are desoldered, you should be able to detach the shield
and lift it up off the board.  Leave the ground wires attached to it
and just set it aside.

Investigation:  Situate the monitor so you can work behind it and still
see the picture at the same time, reflected in a mirror (a patio door
or window at night works, too).  Connect your computer to the monitor's
cable, and power everything up.  Keep the kids and pets away!  KEEP
YOUR HANDS AWAY FROM ALL COMPONENTS!  You should now be standing behind
the monitor and seeing your blue/green or red picture reflected in
whatever.  Take your chopstick and begin wiggling the tiny ends of the
components & wires that are poking out of the back of the color board
while watching the reflected picture.  Try to put a little side
pressure on each stub you touch.  You may grasp ONLY the edge of the
color board with your fingers for support.  Be patient!  This can take
a few minutes.  My experience has been if the screen is blue/green, the
bad connection is often in the top right quadrant of the board as you
face the rear of the board (around 2 o'clock).  For red screens, try 9
o'clock.  In time you will find something that miraculously makes your
picture normal every time you touch it.  You have located the problem!

The fix:  Power everything down and put new solder on the connection. 
Make sure you get a nice, shiny connection.  Power everything back up,
just to be sure you're okay, which of course you will be.  You might
want to carefully examine the rest of the connections to see if any are
questionable.  It's much easier to check everything while you're in

Reassembly:  Re-attach the metal shielding box to the color board. 
Place unit screen-down again on a towel.  lower rear cabinet onto unit
enough so you can re-attach the speaker wire.  Snap cabinet rear into
place, reinstall screws & affix swivel base.

Although this sounds like a big operation, it can actually be done in
less than a half hour.  Try to find a repair shop, though, that will
charge you a half hour's labor to fix it.  HAH!

Finally, good luck with your repair, and let me know how it turns out!

Geary Morton <[email protected]>