I've redirected this article because its got some info that applies to all
monitors, plus some Acorn monitors are badge enginered just like Apple.
Martin Wilson 4WL
SAFETY. THIS IS FOR THOSE WHO KNOW WHAT THERE DOING. MONITORS ARE EXTREMELY
DANGEROUS MORE SO THAN ANY OTHER COMPUTER RELATED PERIPHERAL. THERE'S
THOUSANDS OF VOLTS AT THE BACK OF A TUBE EVEN WHEN OFF. THIS IS FOR PEOPLE
WHO KNOW HOW TO MEDDLE/EXPERIMENT IN SAFETY. USE LONG INSULATED TOOLS. LEAVE
MONITOR OFF FOR A COUPLE OF DAYS BEFORE OPENING TO ALLOW VOLTAGE TO
DISSIPATE. WHEN I SAY OFF I MEAN NOT ON AT THE MAINS SOCKET. STILL TAKE
PRECAUTIONS EVEN AFTER TWO DAYS. IF YOU HAVE TO MAKE ADJUSTMENTS WITH THE
MONITOR ON MAKE SURE THERE'S NO CHANCE OF A SHOCK THAT WILL TRAVEL FROM ONE
ARM TO ANOTHER. THATS HOW ELECTRICITY KILLS BY JUMP STARTING YOUR HEART WHEN
IT'S ALREADY WORKING. I.E. STOPS IT. IF YOU NEED TO RESOLDER A LOCATION WITH
A DRY JOINT ESPECIALLY ROUND THE LINE OUTPUT TRANSFORMER WAIT THOSE TWO DAYS
SOLDER, RE ASSEMBLE AND TRY. IF ITS STILL DUFF WAIT ANOTHER DAY OR SO BEFORE
Document : apple-13in-monitor-fix.txt
Revision : 2
Date : 31 Jan 1995
composer : email@example.com
CHANG, Kui Yu (Julian)
AppleColor 13" High-Resolution RGB monitor
Powers itself off sporadically, green power light goes off with switch still
stuck at 'ON' position.
3 SOLUTION 1
Adjust the variable resistor on the _back_ panel of the unit.
- On older models, this is simply the topmost control with a
"mini-sun" icon beside it.
- On newer models, this is accessible only after removing the
case. This resistor is labelled "Cut-Off".
The picture brightness level will vary with your adjustments.
Normally, this solution only works if the problem was caused by a prior over-
adjustment of this particular control/resistor. My experience with a working
monitor is that if this brightness setting exceeds a threshold, the monitor will
power off automatically. Resetting it to a normal level solves the problem.
For my case, this was not the cause and thus SOLUTION 1 did not work.
4 SOLUTION 2
Replace the High voltage resistor.
(the 'RED' block, to be called the 'block' henceforth)
This is the big (about size of 2 cigarette boxes piled), red block sitting on
the bottom shield, with 2 suction wires attached _and_ 2 wires soldered to it.
On it is the part no. 1-230-666-21.
One of the suction wires leads to a suction cap on the CRT(Cathode Ray Tube).
You can('might' for option c) get this from:
a) SONY dealer $66.68 1-800-488-7669
Authentic SONY part # 1-230-666-21
b) Computer Component source $27.99 1-800-356-1227
Fax : 1-800-926-2062
OEM part, discount of $1.00 for qty of 11 or more.
Remember to tell them you want a "Macintosh Replacement Part" :
APPLE MO401 RGB HIGH VOLTAGE BLOCK
After you have specified the above info., the sales assistant might ask
you "Is this a Flyback?". Remember to answer "Yes" although it is not.
Otherwise the salesperson might say "Sorry we don't have the part".
They like to think of this as a "Flyback"
Note 1 : Next day delivery cost $9.90
Note 2 : They do handle International Sales, but transaction amt must
(International Voice no. 1-516-496-8780)
(International Fax no. 1-516-496-8984)
c) Apple dealer
Apple part # 1-230-666-21, ask for # 34-484
Some soldering is required(just 1 or 2 wires)
** Remember, it is advisable not to remove the original block before your
receive the replacement block. You might forget the orientation since the OEM
block doesn't look alike.
I ordered my part from b), which is an OEM replacement.
It has exactly the same functionality/dimension but does not look as pretty.
The replacement comes with a suction wire already connected, you plug the
other end onto the CRT. When removing the original cup, you just squeeze it.
There are 2 suction wires connected to the block, one goes to the CRT
and the other connects to a board component(fly-back).
You'll need to remove the Board suction wire connected to the original
defective block. Trick - push the suction wire against the block and then
release, the wire head has 2 ears that hook on to the gaps in the metal socket,
but the whole thing is pressured up with a spring.
After replacing this part, my monitor was up and working again!
5 ADVICE FROM OTHER PEOPLE
Below are abstracts of what people sent me to help, they should give you a
I recently performed some repairs to my Apple color monitor and thought
that I should share my experiences with the net.
I have an apple hi-res 13" RGB monitor. Lately I've had problems with the
monitor cutting out (turning itself off completely). This symptom is like
that described in an Apple recall, but my serial number was not included in
the recall. According to Larry Pina's book, _The Dead Mac Scrolls_, the
problem can be remedied by adjusting a resistor labelled "cutoff". Making
the adjustment allowed me to use the monitor, but each time I adjusted it
the picture became darker. On the facing page in Pina's book, he tells
about replacing a high voltage resistor, but doesn't indicate if replacing
it solves the same problem as adjusting the cutoff resistor. Anyway, I
decided to replace the resistor. I ordered a new high voltage resistor
From Sony, using the part number in Dead Mac Scrolls. The part, with
shipping and sales tax, was $62. This component is the thing that attaches
to the wire with the suction cup plugged into the CRT. I was a bit nervous
about messing around with the high voltage, but I discharged everything
with a grounded screwdriver. It took me a little while to figure how to
unplug the suction-cup connector (you squeeze it). Then, I had to unsolder
two leads and solder in the new part. That was not too difficult. There
appeared to be some grease under the suction cup, so I used automotive
dielectric silicone grease (for spark plug wires) when I reinstalled the
new part. Finally, I reassembled the monitor, held my breath, and turned
it on. Voila! It worked. I readjusted the cutoff resistor back to its
original setting, to make the picture brighter, and the monitor didn't cut
out. Time will tell if the repair holds, but for right now I'm happy.
I hope these experiences will be useful to someone else.
If your monitor shuts itself off after a random amount of time, one of the
likely sources of trouble is a defective high-voltage monitor. This was
covered until March 31 by an unannounced warranty, but no longer.
Before you give up hope, get Larry Pina's book, Macintosh II Repair &
Upgrade Secrets, and read pp. 53-54 for a quick fix anyone can do in 10
minutes that may save you an expensive trip to the shop.
I have repaired dozens of these. There are three common causes for the old 13"
monitor shutting off. two described by Pina, one not.
Symptom: Monitor appears to shut off. Green power light goes out.
1) Adjust the cut-off a smidgen. Described by Pina. Never seen it help.
2) Replace the High voltage resistor block, Sony p/n 1-230-666-21. Has always
fixed this problem.
Expensive part and hard to find. I have 4 left from my old service shop
days. I'll sell 3 for $50 each. Requires soldering.
Computer Component source, 1-800-356-1227, has these for $26.99
Alternate Symptom: Monitor goes black or remains black at power up. Green power
----------------- light stays on.
Good News: No parts cost. Not documented by Pina. This is usually caused by
cracked solder joints on the small PC board that plugs into
the back of the CRT. Touch up the solder joints, and you're back in business.
Please don't mess with any of this unless you are an experienced hardware
technician with the required skills.
The color screen can retain a 45,000 volt charge if the bleeder resistor is
broken, and can kill you if you have a weak heart.
I do mean to scare you. This really can be dangerous if you do not know what
Jerry StubbsAndy Seligman
The capacitor a stand alone component that is attached to the bottom shield.
It ties directly into the flyback and then into the CRT. No mistaking it....
It's rectangular in shape and red in color..... It also has one other cable
assy that plugs into the main logic board. Dealer cost for the part is $50.00
but they may not sell it to you. It's suppose to be installed by an
authorized tech so usually it will not be sold over the counter.
Roy H. Robinson
Thanks to :
firstname.lastname@example.org.CH Wolf Christoph
email@example.com David Allan
firstname.lastname@example.org Andy Seligman
Roy_H._Robinson@onenet.com Roy H. Robinson
email@example.com Jerry Stubbs
firstname.lastname@example.org Kung Chyun Tang
and all who helped.
I submitted this article as I thought the technical info contained may be of
interest to a wider non apple audience. Some Acorn monitors use the same
guts as Apple monitors anyway. Martin Wilson 4WL