16.008 Suddenly my monitor has an all-blue (all-red, etc.) screen! How do I fix this?
Description
This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
16.008 Suddenly my monitor has an all-blue (all-red, etc.) screen! How do I fix this?
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.
A more detailed procedure is presented below ....
1. The part that causes the problem when it fails is a "choke" or "inductor" ,
it is mounted on a small circuit board attached to the back of the monitor tube
itself. This part looks like a small blue ceramic ball with two leads coming
out the bottom, and is color coded for 10 microhenries.
2. There are three of these items on that circuit board, and if any
one of them fails, the symptom is a screen all of one color, with
total loss of any controls of the monitor. The parts are identified by
number, and what color the screen is will tell you which one to
replace.
L6R2 for a Red screen
L6G2 for a Green screen
L6B2 for a Blue screen
3. You can probably get a 10 microhenry choke at Radio Shack, or it is
available for $1.28 (plus a $5 Handling charge) from Digikey Corporation at
(800) 344-4539. They take Mastercard, Visa, and C.O.D.. The Digikey part
number is M8025-ND.
4. After replacing this part, the monitor colors may need to be readjusted via
the small color trimpots on the same circuit board.
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