SUMMARY: 3/50 Monitor Failures/Repairs

From: Steve Simmons (
Date: Fri Oct 18 1991 - 22:55:08 CDT

Sun-Managers is a funny list. At 18 hours and counting, I'd had one
(count it, 1) response which said "don't fool around with high voltage
unless you know what you're doing." At 19 hours another 8 or 9 messages
dropped in, between them containing all the data I could possibly need.

Summary point 1: DO NOT do this yourself unless you know what you're
doing. Ian's article says that, most of the respondents say that. I
would not do this stuff myself. We have qualified electronics techs
who merely need to be told what is to be done.

Summary point 2: The article I was searching for by Ian Darwin
was found by (ta-da!) Ian Darwin (

>>Second, I am looking for an article I could have sworn was written
>>by Ian Darwin in "Sun Expert" about how to diagnose and replace a
>>flyback. Can anyone point me to it?
>If anybody can, I should be able to. The article appeared in the July, 1990
>issue, on page 80. Its title is "A Shock in the Dark." The issue cover
>is a take-off of a hollywood movie set seen from the camera, with the
>storyboard about to be clapped down, as in "Take 8". (This ties in with
>the lead article, on Suns in Video Production). Look for the word Video
>in red on the spine.

It's in the library at work, so off I go.

Summary on "doesn't power up" failure mode:

Again, from Ian:

>scs writes:
>>Do these things have an internal replaceable power supply?
>Well, yes, it is replaceable by looseingin 4 screws and unplugging it.
>But Philips won't service them. You're likely to wind up cannibalizing
>one monitor for spares anyway, so get one with a working power supply.

Kevin Drysdale ( and Brian Bartholomew
( both noted that the power supply was a separate
item. Bartholomew added:

>I've seen that symptom before, but never successfully fixed it. Yes,
>the power supply is on a separate board.

Summary on "one stays blank and emits a high-pitched squeal":

Several respondents pointed this out as being the "canonical" flyback
failure mode. I will note this contrasts with several earlier postings
to Sun-Managers which call "smoke and ugly smell" a symptom of flyback
death. Both could be right -- I've not left the squealer plugged in
for more than a minute or two.

Kevin Drysdale ( was quite specific on the
topic, supplying a bit more data:

>The high-pitch squeal is the flyback. Replace the flyback and if it
>persists, then replace Q231 (the transistor on the heat sink). You can get
>the flybacks from CRC for about $38 each. Their number is 1-800-366-1272.

Summary on "minor case of left-right jitter which comes and goes. When
 it starts, a quick boot to the head fixes it.":

Again, from Ian:

>Problems that go away with a "quick boot to the head" can mean dirty
>contacts on some control (vertical adjust, etc.) or physical failure of
>some component. The adjustments are internal controls and can be
>cleaned with the appropriate contact cleaner spray but, again, USE
>CAUTION when working inside as high voltage can be present for a LONG
>time after you remove the power cord from the rear of the unit (you
>always do this before removing the cover, don't you?).

Bartholomew ( added:

>I haven't seen that symptom before. Look for a loose connection by
>wiggling the plugs with a non-conductive plastic tool.

Summary on "worst left-right jitter ever seen":

This was the only one Ian didn't know how to fix (guess he's mortal
after all :-)

Mark Galbraith ( suggested that this too was a symptom
of dying flyback.

Kevin Drysdale, "Lead Field Engineer" ( was quite
specific in a different area:

>Your screen edge jitters are caused by capacitors C205 & C209. Replace
>them. They are 10uf 50V caps.

This was echoed by russ moritz (

>You may be able to get by for a short time by adjusting the horizontal
>freq. pot, but after a while they started failing again for us. I
>found by replacing the two 10uf caps, C205 & C209, below the horizontal
>center & horizontal frequency pots solved the problem on most all of
>our 3/50's.

Many thanks to all:

Ian Darwin (
Brian Bartholomew (
Andrew Luebker (
Mark Galbraith (
Kevin Drysdale (
Russ Moritz (russ@mayo.EDU)

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