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From: wolfgang@wsrcc.com (Wolfgang S. Rupprecht)
Newsgroups: sci.electronics
Subject: Re: Sony TV Hi-Pitch squeal
Message-ID: <1991Jun13.160527.4094@wsrcc.com>
Date: 13 Jun 91 16:05:27 GMT
Article-I.D.: wsrcc.1991Jun13.160527.4094
References: <6298@ns-mx.uiowa.edu> <1991Jun3.150425.4892@news.larc.nasa.gov> <1991Jun3.163755.825@hubcap.clemson.edu> <50186@ut-emx.uucp>
Distribution: usa
Organization: Wolfgang S Rupprecht Computer Consulting, Washington DC.
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> 	Another common problem that causes that squeal is dust on, in, and
> around the flyback and the anode cable. Apparently the dust is attracted 
> to any leakage, and this gives a convienient path for small arcing to 
> form. I know I cleaned off the cables on my 1982 RCA, and it has been silent
> for a long time now. By the way, before you clean it, make sure you aren't 
> grounded, and that the set is unplugged. 

Being grounded in the formal sense or not doesn't matter AT ALL when
we are talking about 10's of kV.  If you happen to touch the HV
section on your TV, and it is still charged up, you will get knocked
on your butt.  Perhaps permanently.

> If possible, short out the anode 
> cable to the chassis ground first. People do funny things when hit with
> this kind of voltage ( I didn't, but I'm a Tech ).

If possible????  You are kidding, right?  BY ALL MEANS ground the HV
capacitor to if you are planning on messing with the HV section.
Especially if you are planning on wiping the HV lead with a damp
cloth!  Keep the shorting strap in place during the whole time you
work on the set.  Charge will bleed back from the glass parts of the
CRT onto the internal capacitor plates.

Remember these simple rules when working around HV:
		
	1) Keep your left hand in your back pocket.  This way you
	   won't be tempted to use it and complete a circuit should
	   you drop something and reflex action causes you to make a
	   grab for it.

	2) Always attach a ground wire to a well connected metal part
	   of the device.  You will obviously want to attach the
	   ground end of the wire first.

	3) Now attach the ground wire to HV capacitor - you will hear
	   a snap if it was really charged up.  If it only had a few
	   kV's on it you probably won't hear the snap.  Leave this
	   ground attached till you are done!

-wolfgang

PS. I have had excellent results with RTV, and/or Crazy Glue for
    fixing loose parts that have caused H-sweep squeal.  Crazy glue
    works like a champ at re-laminating loose flyback parts.  RTV
    really absorbs the high frequency energy that still happens to
    make it out.  Together they are a great combination.

-- 
Wolfgang Rupprecht    wolfgang@wsrcc.com (or) uunet!wsrcc!wolfgang
Snail Mail Address:   Box 6524, Alexandria, VA 22306-0524