Sony CRT monitor GDM-F520: Crackle noise and red flashs after poweringon

[Steffen Moser]

Hi all,

I've got a problem with my 21" CRT monitor "Sony GDM-F520".

I've been using this device for about eight hours per day since
I bought it in November of 2001 (it was manufactured in September
of 2001 as the type label states).

The monitor has been working all over the time without any
problems, the quality of the picture is still excellent (very
high purity). My OSD brightness and contrast settings are both
at about 50 %. I didn't have to increase them much, yet.

But for about a few weeks I have noticed the following problem:

Although the monitor itsself does still work perfectly (i.e.
it displays the picture as usual), I can sometimes hear a kind
of "crackle" noise (not very loudly!) immediately after warming
the monitor up (it takes about 10 to 15 seconds) after powering
it on.

Together with this crackle noise the picture is flashing in red
color.

It doesn't happen regularly and if it happens, it won't happen
more often than about one or two times - and only after powering
the monitor on (or leaving the energy saving mode). I haven't
noticed it during operation, yet. It seems to me that it
especially happens when the device hasn't been in use for some
hours (i.e. has been cold).

I think I should add, that the monitor has always been making
gentle crackle noises after powering it on or off (as it did
almost every CRT monitor or TV set I dealt with). But the red
flashing which goes together with the noise haven't been until
it appeared the first time a few weeks ago.

My questions to you would be:

- What could that problem caused by? For me, as a layman re-
garding monitors' and CRTs' internals, the noise sounds like
a eletrical discharge (as if very little sparks are jumping
over). I have tried to look through the louvers (having the
room darkened), but I didn't see any sparks but only the
glowing of the CRT's heating.

- Is this maybe a common problem with the Sony GDM-F520 or
other Sony CRT series?

- Do you think that the appearance of the problem will increase
and it's a "omen" of the monitor's soon death?

- Do you think that bringing the monitor to a repair shop (or
even to Sony's service) is a worthwhile thing?

- Is there anything that I can do myself? At least, I can
imagine that the discharges could be caused by dust. Is this a
typical problem and would dust let the monitor react that way?
So, do you think that there a good chances that opening and
cleaning the device can solve it?

I'll appreciate any help and thank you very much in advance!

Best regards,
Steffen

 

[[email protected]]

I would open the case and check the high-voltage with a HV-probe. It
should be about 27-28KV, although some may go up to 30 KV. Some
monitors have a small adjustment pot to control the HV. I would set it
about 28 KV.
Also make sure that the are around the HV anode connector on the tube
is clean. Some use aa dielectric grease under the anode cap to reduce
the chance of arching.
John

 

[Ray L. Volts]

I think I should add, that the monitor has always been making
gentle crackle noises after powering it on or off (as it did
almost every CRT monitor or TV set I dealt with). But the red
flashing which goes together with the noise haven't been until
it appeared the first time a few weeks ago.

The snap/crackle/pop is called corona discharge (a.k.a. arcing). In its
mildest form it isn't a concern.
You sometimes have to open the case, turn down/off the room lights and look
around carefully to see the more severe and localized cases. The usual area
for arcing is around the high-voltage section (flyback transformer area, in
particular).
My NEC FP2141SB is a top-of-the-line 22" monitor and it began very minor
arcing a year after purchase! So, sticking with good brands and top models
doesn't avoid arcing.

Arcing usually results from insulation breakdown (potting, flyback case,
etc.) or voltages gone awry due to component malfunction (including going
way out of tolerance due to age). It's really only a major concern if the
unit develops others symptoms, as is your case, or if the arcing becomes
alarmingly loud and/or highly visible, in which case the unit is not far
from developing other symptoms. The red flashing could be a result of the
arcing condition creating probs in another section, such as the screen
drives or bias, etc.

First thing to do is fix the arcing. If that cures the red flashing,
hurrah! If it doesn't, at least the arcing is fixed and you can move on to
the other problem. Once you locate the exact points of arcing, you can coat
the area with one of the many products made for the purpose. Depending on
the accessibility of the area, techs will use a high-voltage putty compound
(usually silicone) or thick paints like Glyptal resin (GC Chemicals calls it
"GLPT"). GC offers several products for controlling arcing -- see:
http://www.action-electronics.com/gcelect.htm#Chemicals

Whatever you use, you want to cover any and all sharp/protruding points near
the area of arcing, as well as, obviously, any insulation which appears
defective or missing.

- Is there anything that I can do myself? At least, I can
imagine that the discharges could be caused by dust. Is this a
typical problem and would dust let the monitor react that way?
So, do you think that there a good chances that opening and
cleaning the device can solve it?

Dust buildup alone isn't a common cause of arcing. I've worked on sets with
thick carpets of dust in them and NO arcing, and sets that were practically
factory clean with severe arcing. The most common causes of arcing are poor
design and/or manufacture and insulation breakdown due to age or
environment.

Be very careful if you take the unit apart. There are many areas of lethal
potential in a CRT monitor, even long after you unplug the unit. Don't
touch any exposed metal. Don't wear a metal wristwatch or rings. Many
injuries are not caused directly by electrical shock, but by the
individual's reflex reaction as s/he quickly moves his/her arm trying to get
the hell out of there when s/he hears or feels a static discharge or minor
shock. You can get all kinds of cuts, scrapes, abrasions and bruises on the
various sharp edges inside these things. Plus, if you happen to slam your
hand against a more fragile part, you've just created an even worse
situation than you were trying to remedy.

If you open it up and find heavy deposits of dust, first try blowing it
clean with an aerosol duster. Blow it out and away from the unit and try to
avoid blowing deposits into crevices or under components. If air dusting
alone doesn't remove the thicker deposits, use a nylon brush (plastic or
wood handle only) to break them loose then blow them out. You really
shouldn't need to disconnect the various cables and remove the main board --
handling the board can be very hazardous and is best left to a pro.
Remember to unplug the unit and don't use any conductive cleaners.

If eliminating the arcing doesn't cure the red flashing symptom, get back to
us.


Good luck,
Ray

 

[PainintheAmp]

Hi Steffen.....Try this...UNPLUG the thing from everything else...Take
the back off...let it set a while to discharge any latent high
voltage...Get a can of Dust-off or similar compressed spray ( CO2 or
nitrogen ) ..Spray all around the HV section in the monitor ( usually
it has metal shields around it) make sure the thick red wire going to
the tube and where it plugs into the tube is free from dust and such.
and PLEASE UNPLUG the thingy first..or else you'll be saying more than
OUCH..Im sure