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From: durham@w2xo.pgh.pa.us (Jim Durham)
Newsgroups: sci.electronics
Subject: Re: Sony TV Hi-Pitch squeal
Message-ID: <163@w2xo.pgh.pa.us>
Date: 8 Jun 91 23:59:11 GMT
References: <6298@ns-mx.uiowa.edu> <1991Jun3.150425.4892@news.larc.nasa.gov> <1991Jun3.163755.825@hubcap.clemson.edu> <1991Jun7.030706.85@cmkrnl.uucp>
Reply-To: durham@w2xo.pgh.pa.us (Jim Durham)
Distribution: usa
Organization: Jim's Basement, Gibsonia, PA
Lines: 45

In article <1991Jun7.030706.85@cmkrnl.uucp> jeh@cmkrnl.uucp writes:
>In article <1991Jun3.163755.825@hubcap.clemson.edu>, 
>falcon@hubcap.clemson.edu (james lysaght) writes:
>> I researched the problem (i'm an Electrical Engineer).  My TV is solid state 
>> so I only researched solid state and will only comment on those.   Every 
>> solid state TV has a little transistor (little as in microchips) which 
>> serves to prevent this squal.  
>
>Rubbish.
I agree, although I would have phrased it differently! 8-) .
>
>> The squal occurrs when, over time, the transistor burns 
>> out and no longer functions.  
>
>Rubbish
Now c'mon...little squeal suppressor? I've got my pants legs rolled up..but..
>
>horizontal-sweep squeal (note spelling) can be very difficult and expensive to
>track down and fix... particularly since many technicians can't hear it!

I have to deal with these things on a regular basis. The way I find
the offending part is to use a rolled-up sheet of paper or a drinking
straw. It is pretty directional at 15khz and , if you put one end
in your ear (carefully!) and wave the other end around the vicinity
of the flyback and horizontal output components, you should shortly
be able to discover the component that is squealing. Most times it
is the flyback transformer. I have seen these fixed by driving small
wooden wedges in between the winding and the core.

Yes..a lot of people can't hear 15 khz. These are probably the same
ones who go around worrying about "aliasing noise" on a CD 8-) ! .

One other thing. If the picture is not tearing or unstable, the above
advice is useable. If there is a multi-frequency sound to the squeal
(low frequencies mixed in with the 15khz), then you could have
a horizontal oscillator problem. The flyback will not like foreign
frequencies and will protest. However, you should see some indication
of this in the picture. If you *do* have a "dirty" sounding squeal
and picture problems, then the only thing is to get out a scope
and look at the horizontal waveform and see if it is a nice clean
sawtooth. If not, fix the oscillator or output stage. This phenomenom
is called "sqeegying" of the oscillator by tv tech types.

-Hope this helps.
Jim Durham (durham@w2xo.pgh.pa.us)