Just in case someone has some ideas: the monitor on this system (an XT clone,
the monitor is Packard Bell mono, & it has a herc-compatible card) has
started to get really flaky.  This is still intermittent, but getting worse.
It's as if it starts shifting horizontally, shivering, really, very rapidly
& **very** violently.  Lately I'm even noticing some sort of noise as it
does it.  ("Static" doesn't seem quite right, but I can't think of a better
description.  Very faint.  From inside the monitor, I think.)

At first it seemed to be almost always shortly after powering up.  Now it
doesn't seem to have any pattern.

Any likely off-the-cuff diagnoses?  And what is the likelihood that this
can be fixed cheap (free) by a 10-thumbed hardware-know-nothing?

(It has started doing it as I've entered this - if my typing is bad, it's
because I'm doing this almost blind.  I can see where the lines are, more
or less, & sort of how long they are - and from time to time it snaps back
into focus briefly.  Long enough to do some correcting.)

25 responses total.

I would wonder whether the high voltage is starting to arc across
accumulated grung. It could also be in the fly-back x-former (uh oh).
Open it up and look for loose connections and/or *char* (any smell,
yet?).
Say, I have a flaky XT monitor too. Let's see - did I mention this here
before? Picture suddenly disappears *except for selected colors* (RGB
monitor). Still doing it intermittently. Now I remember - I was supposed
to open it up and check the intensity pot connections/wiper. And look
for char too, I guess 8-<.

REcognize that HV is well insulated, and open the thing. Get it
running and use a WOOD stick (not a pencil) to tap on various 
and sundry parts. Since this is an intermittant (the most damnable
problem) the shakey part should reveal itself with physical agitation.
  
Include wires in the tapping routine.
  
Same goes for aa8ij's monitor problem, btw.

My Apple MultiScan 15 monitor (which I got from PropDisp for $25)
is now losing red, intermittently. That is, it is "flashing" blue, and
then back to normal. Is this likely to be something that can be corrected
by poking its innards with a wood stick, or blowing out the dust, or
are more drastic actions required? 

(A previous problem with the my original MultiScan 15, where the picture
broke up and flickered, was due to a problem in the video driver, which
was fixed by reinstalling it. Could this very intermittant color
problem be in the driver too?)

Doubtful.  It sounds more like a hardware problem; loose connection or
some such.  This could actually be anywhere, in the computer, the cable,
or the monitor.  If you can swap monitors and cables, and see what the
problem follows, you should be able to narrow down the location.
Wiggling cables and connectors may also help in terms of locating the
problem.  Blowing the dust out of the monitor probably won't help (and
could make the problem worse) but taking the cover off and looking for
loose cables or connections could well help.  Blowing the dust off may
be helpful in terms of wiggling cables and looking for obviously crufty
solder joints and will certainly make the job more pleasant.

I have wiggled connectors, but it still has the blue flashes. Next,
back to the old monitor.

It sounds like an intermittent.  I'd pull out the PC board and re-do
several of the solder joints.  Especially those for heavy components
with thick leads.  Even a joint that looks good to the naked eye can
be bad. Also touch up all the joints to connectors on the board.

**************


Warning!  High Voltage, even with power off!!!


**************

(well, somebody had to say it)

Point taken!

The way it now flashes back and forth between normal and blue is almost
entertaining. It spends about 50% of the time in each mode, but the
flashing seems rather random, at an average interval of about 10 seconds or
so. It should be possible to deduce something from this. Right - a poor
connection somewhere. 

My Dell 15" monitor loses blue every so often as well.  It usually comes
back when I whack the side of it.  I know what the problem is; the socket on
the CRT has loosened up again.  I need to epoxy it or something,
because the problem comes back every time I move the monitor.  I just
haven't gotten around to taking it apart again, this time.

Just tried "wacking", without effect. Between the flashes of blue there
are much less discernible rapid fluctuations in color sometimes, like
'static'.

re #0: This sounds like your monitor's dying breaths, take into
consideration that you might have to get a new monitor if all else fails.
besides, you should feel luck to have a monitor survive since the XT days-
it's probably 10 years old? i've seen monitors die after 3-5 years. it's
probably not worth repairing such a monitor since you could prolly get a
better one for less then the repair costs.

re #3: Rane, this sound very much like a cable problem. try wiggling the cable
where it connects to the monitor or computer. if that doesn't help, try
replacing it with a known good cable. if it still doesn't help, try checking
that the plugs on the monitor and computer are working (no broken pins/blocked
pinholes, make sure it is soldered well to the graphic card and monitor
internals, etc.). if all else fails, try taking a look at the inside of the
monitor.

I think it's worth trying to fix.  I think his Apple monitor has a Sony
Trinitron tube in it.  They are nice monitors when they work. (I have 2.)

Breaking news....I substituted my other MultiScan 15 and while the
color came up OK, the problem I had had last October, of a wildly fluctuating
display, began. It was cured that time by reinstalling the ATI video
board software, so I uninstalled the old software and attempted to
reinstall it (with the monitor on the Apple CPU port). However the
installer said "No ATI retail hardware installed". I removed and
reseated the board, without success. It MAY be that the two problems, though
different in the different monitors, reflect a fault in the video board.
I have written ATI. (I have not yet tried the monitor with the bad red
on the CPU port....next test.)

I've been meaning to ask - how do I open a MultiScan 15 case, if I
do find there is a problem with the 'bad red' monitor? There are no 
screws, just two tiny slots at back of the top of the case, and I
can't see what's in there. The slots are too small for an ordinary
screwdriver.

I forget exactly but Apple likes to use little, locking, plastic taps.  You
have to get some skinny tool between the plastic halves and lever them apart.

I have some crowbars...for watches...

A letter opener works well.

The previous owner of a Mac 512K I used to have lacked a long-handled Torx
driver or a "case cracker," both more or less required to open old Macs.  He
solved the problem by knocking out one of the top vents with a hammer, then
hacksawing around the case seam.

Those screws are just T-15 Torx screws.  I just got a Torx driver, cut the
shaft in half, and epoxied in a length of tubing to extend the tip.

I think the red drop-out problem is a capacitor in the red driver 
circuit that has lost it's elecrolite juice due to age and is arcing 
inside itself.  As it does this it heats up and drives out more 
electolite.  This is fixable.  Find the one with the swollen top and 
replace it.  'Course I'm sure you don't have it anymore as late as I'm 
posting, but fyi.

Now you tell me.....  8^}  Well, that monitor was taken to recycle over
a year ago. But I'll keep that in mind. One thing that makes me
wonder about your diagnosis, however, is that this became a known
problem with that model of monitor, and *it was always the red gun*
that failed intermittently. I would think capacitors likely  to fail
would be going into all the drivers, not just the red  ones.

Maybe the red one was closer to a heat source?

Very possible, or some other differences between the driver circuits.

The heat source would be my guess as well.  Too bad that these things
aren't better considered at design time/cost-benefit time.

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