3/50 Monitor Failures/Repairs
2007-12-25 7:28:00
(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 (ian@sq.com):
>>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 (kd@redwood.cray.com) and Brian Bartholomew
(bb@math.ufl.edu) 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 (kd@redwood.cray.com) 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 (bb@math.ufl.edu) 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 (mark@deltam.com) suggested that this too was a symptom
of dying flyback.
Kevin Drysdale, "Lead Field Engineer" (kd@redwood.cray.com) 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 (russ@mayo.edu):
>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 (ian@sq.com):
Brian Bartholomew (bb@math.ufl.edu)
Andrew Luebker (aahvdl@eye.psych.umn.edu)
Mark Galbraith (mark@deltam.com)
Kevin Drysdale (kd@redwood.cray.com)
Russ Moritz (russ@mayo.EDU)
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