monitor blacks out

[[email protected]]

This computer monitor will show a momentary, thin horizontal glitch
shoot across the screen. This happens a few times per hour. For several
weeks now, and occurring about once every couple of days, the screen
will suddenly go completely black. When that happens, I turn it off for
an hour or so and then it will function okay again. The occurrence of
the blacking-out is getting more frequent. It now happens 2-3 times a
day.

What would be the likely cause? Thanks.

(I had previously asked on this group about how to open the case. A
littler prying solved that problem. The switch seems okay. I cleared
the small amount of dust inside. There was no burnt smell anywhere. And
yes, I did leave it unplugged overnight before opening the case, and
test for spark anyway.)

 

[Charles Schuler]

This computer monitor will show a momentary, thin horizontal glitch
shoot across the screen. This happens a few times per hour. For several
weeks now, and occurring about once every couple of days, the screen
will suddenly go completely black. When that happens, I turn it off for
an hour or so and then it will function okay again. The occurrence of
the blacking-out is getting more frequent. It now happens 2-3 times a
day.

What would be the likely cause? Thanks.

If you mean a thin horizontal line and if it is a cathode ray tube monitor,
then the vertical deflection circuit is failing.

 

[Richard Rasker]

Op Wed, 22 Nov 2006 08:14:56 -0800, schreef herb_k:

This computer monitor will show a momentary, thin horizontal glitch
shoot across the screen. This happens a few times per hour. For several
weeks now, and occurring about once every couple of days, the screen
will suddenly go completely black. When that happens, I turn it off for
an hour or so and then it will function okay again. The occurrence of
the blacking-out is getting more frequent. It now happens 2-3 times a
day.

What would be the likely cause? Thanks.

This sounds like bad solder joints, most probably in the horizontal or
vertical deflection circuitry. Inspect the pcb's solder side, and in
particular larger components (coils, connectors, TO220 transistors), and
components attached to a heat sink. Look for a sort of "crater ring"
around component pins; here's a clear example:
http://www.linetec.nl/electronics/badsolder2.jpg

Hope this helps, regards,


Richard Rasker

 

[[email protected]]

Op Wed, 22 Nov 2006 08:14:56 -0800, schreef herb_k:


This sounds like bad solder joints, most probably in the horizontal or
vertical deflection circuitry. Inspect the pcb's solder side, and in
particular larger components (coils, connectors, TO220 transistors), and
components attached to a heat sink. Look for a sort of "crater ring"
around component pins; here's a clear example:
http://www.linetec.nl/electronics/badsolder2.jpg

Hope this helps, regards,


Richard Rasker

absolutely right, it helps

After reading Richard's reply, I figured that when the screen blacked
out again, I could whack the case. That repeatedly brought the raster
back in the following days, and also indicated the loose connection.
Today, I finally opened up everything and examined the circuit board.
After a long time looking, I found a solder joint looking just like the
ones in Richard's example photo. It was underneath the transformer.

It was surprsingly easy to melt the existing solder. Some got wicked up
inside the hole, which seemed good. I also added some more solder. When
I reassembled and reconnected, I had to adjust horizontal and vertical
size and position - so that tells me I probably have indeed resoldered
the right connection. Raster is now stable so far, too.

It feels really good to repair something and have it all go well.
You've got to love this group Merry Christmas, everybody.

 

[Herb]

[this is a followup from December: my monitor circuit board had a
loose solder joint. I re soldered it, and that fixed the problem of
blacking out]

This week very similar symptoms re-occurred. I found yet another loose
joint! I fixed it, and re-soldered some nearby joints as a
preventative measure.

It occurs to me that if I produced and sold defective crap like this,
I'd end up losing my house. Why was there no class-action suit against
these board makers? Why was there no suit against the similar massive
situation of bad-capacitor producers? Are they immune because they are
in Asia. I'm getting tired of defective crap.

 

[gengiskanhg]

I have an AOC Spectrum 4V 13" Monitor.
Since one year it has been blacking out (turned off the display) time
to time.
It has been "turned on" with a hit.
Few weeks ago the problem had getting worse. The black out problem has
been more common and the "hit" to turned it on should be stronger (A
strong hit in the upper or bottom front of the monitor is the best).
Sometimes the displays turned more green than normal. When it is hit
some "click" sound is listened before it turned on (when it turned
on).

Some times when it black out the power leds blinking some times,
sometimes they are normal and response to (Func, + and -) buttons. And
in other times leds are die (turned off).
I open the monitor and looked out for cold solders joins or bad
capacitors (with the eye, for example capacitor with its contains out
(dielectric))
I found some bad solder joints in the NECK BOARD but Multimeter told
me there was continuity there. I resoldered them to be sure and to
prevent more problems.
After that, leds and front bottoms work property. But only for a
while. The problem continue. Some night it works and the other night
it do not display anything without any change, any move or anythig
more than push carefully the on button.

I realize that if you give a little hit in the NECK BOARD display
sometimes is turned on and if it is turned on it become more green.
After I have resoldered many suspected joints, I try to found the
problem part with little hits in the NECK BOARD components. But it
doesn't seems to work.

***Hitting the board in many parts give the same result. If I take it
with my hand an move it a little, nothings happens. But if I hit it,
displays is changed as I said.
***¿Is it normal?

I realize that electrolytic capacitors NECK BOARD areas have a little
more sensibility to a hit.
***So I one to ask you if you thing I should change all the
electrolytic capacitors

The question I have after read quickly the monitor repair guide...
(http://www.repairfaq.org/sam/monfaq.htm)

....with the knowledge that the "click" like sound is maybe the flyback
turning on sound and with the behavior of the neck board I do not know
exactly what to do.

Thanks very much for any help.

Regards.