mickhayafe
TV Repair Authority
Apr 5, 2003, 6:50 PM
Post #2 of 2
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Re: [gary] High Frequency Noise
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that high frequency is the 15khertz horizontal frequency, what is happening is the high voltage transformer (flyback) or a coil in the horizontal output circuit is vibrating giving you that hum. It can also be the yoke (coil that sits on the neck of the tube).
what i use to cure this problem is can spray varnish, i buy mine at home depot (even though i don't like the service) i searched for a picture of the can online and got a picture. here's the link
http://www.pinrepair.com/restore/pf0.jpg
you need to coat the transformer, any coils you see and the yoke evenly on all sides making sure you get the top sides and (especially on the flyback) gets to the bottom. do it while the tv is unplugged, (don't bother trying to listen for where it's coming from, it's pointless)
NOTE: do not spray anywhere near any push buttons because they will solidify and you will have to replace them. seeing as the high voltage is usually near the back of the tv, this is typically not a problem, just don't go berserk. to avoid this use the spray nozzle that is provided, this will give you more accuracy. (this nozzle is one time use because it's very hard to clean out after you use it)
if you want to make sure the varnish that you buy is non-conductive, (which is really important) you can buy a can it's only like $4. spray a puddle on a piece of paper (watch it cause this stuff is sticky, ie, not on a carpet, etc) and take an ohm-meter to it. stick both ends in the puddle (making sure the probes are not touching of course) and if you have continuity then don't use it.
after you spray all of the above you will have to wait 24-48 hours until it completely dries and it takes about 3-4 days for the smell to go away, so i would recommend you do this w/ a fan going and the windows open to minimize smell.
i know i gave you alot of stuff here so if you have any questions don't hesitate to ask.
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