1. Home
  2. Electronics Repair
  3. Sony CRT monitor GDM-F520: Crackle noise and red flashs after powering on

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

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

Reply to
Steffen Moser
Loading thread data ...

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

Reply to
jdgill

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:

formatting link

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.

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

Reply to
Ray L. Volts

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

Reply to
PainintheAmp

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.