Sony TV Hi-Pitch squeal
Francis Fang
when I've noticed that there is a semi-loud high pitch squeal that accompanies
the operation of the set. Does anyone out there have any suggestions for
probable cause?
Thanks in advance.
james lysaght
A high pitched squal is a common aging problem in electronics. The past two
TV's I have owned have had that problem but they lasted closer to 5 years.
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. The squal occurrs when, over time, the transistor burns out and no longer functions. You are correct in saying it is the verticle sweep but you can not stop the verticle sweep oscillation (and still have a picture). So, the
remedy... buy a new TV. It is cheeper to replace than fix (usually).
Disclaimer.... this all based on the idea that your high pitched squal is the same as my high pitched squael (notice I can't spel squael, squeele, or whatever)
Jim Lysaght
j...@cmkrnl.uucp
> 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.
> The squal occurrs when, over time, the transistor burns
> out and no longer functions.
Rubbish.
> remedy... buy a new TV. It is cheeper to replace than fix (usually).
You might actually be correct here, unless the set is very expensive.
horizontal-sweep squeal (note spelling) can be very difficult and expensive to
track down and fix... particularly since many technicians can't hear it!
rec.video has had several accounts from people who reported that their tv is
making a high-pitched whine, but techs could find nothing wrong. (A tv tech's
high-frequency hearing deficiency is likely due at least partly to working
around tv sets day in and day out!)
The source may be the flyback transformer, the deflection yoke, or even a
printed circuit board (not necessarily components on the board, but the board
itself). Someone else mentioned capacitors.
Once you find the offending part, then what? If it's something like a
capacitor or a PC board, you may be able to tie it down or wedge it or
something so that it can't vibrate. If it's the flyback or deflection yoke,
replace it. Some people have suggested potting these components, but this is
not a good idea; they would run very hot afterward and so have a vastly
shortened life, meaning that you'll end up doing the replacement anyway.
Oh, and it's the horizontal sweep, not the vertical. The vertical is at
60 Hz (well, 59.93) and in no way could be considered "high pitched". But
it too is audible in many sets, as a low-pitched buzz.
--- Jamie Hanrahan, Kernel Mode Consulting, San Diego CA
Chair, VMS Internals Working Group, U.S. DECUS VAX Systems SIG
Internet: j...@dcs.simpact.com, hanr...@eisner.decus.org, or j...@crash.cts.com
Uucp: ...{crash,scubed,decwrl}!simpact!cmkrnl!jeh
Allen Kitchen
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. 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 ).
allen
Jim Durham
>In article <1991Jun3....@hubcap.clemson.edu>,
>fal...@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.
>
>> The squal occurrs when, over time, the transistor burns
>> out and no longer functions.
>
>Rubbish
>
>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 (dur...@w2xo.pgh.pa.us)
Timothy T. Rueger
>horizontal-sweep squeal (note spelling) can be very difficult and expensive to
>track down and fix... particularly since many technicians can't hear it!
>
>printed circuit board (not necessarily components on the board, but the board
>itself). Someone else mentioned capacitors.
>
>Once you find the offending part, then what? If it's something like a
>capacitor or a PC board, you may be able to tie it down or wedge it or
>something so that it can't vibrate.
And that is exactly how I solved my particular TV squeal. I found the
offending part, and wedged a wooden clothespin (!) between the part and the
picture tube. A low-tech solution if ever there was one. When it
fails, I'll finally break down (ugh...) and get a new set.
> --- Jamie Hanrahan, Kernel Mode Consulting, San Diego CA
-Tim
_______________________________________________________________________
Tim Rueger - TA, 6.775 - Analog MOS Design
Office: 24-312, 258-5691 Email: ttru...@athena.mit.edu
Home: Westgate 1609, 494-9414 ttru...@ed.mit.edu
Wolfgang S. Rupprecht
> 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 wolf...@wsrcc.com (or) uunet!wsrcc!wolfgang
Snail Mail Address: Box 6524, Alexandria, VA 22306-0524
j...@cmkrnl.uucp
>> 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.
I highly agree with your basic point -- that you should ground the HV lead --
but I'm not sure what "capacitor" you're talking about here. The CRT in a tv
set *is* the HV capacitor. The second anode coating on the inside of the
"bell" of the CRT, plus a similar, grounded coating on the outside, forms the
capacitor. (Not much capacitance, but extremely high voltage and low leakage.
Those who remember the static electricity parts of Physics 101 will note the
resemblance to an old-fashioned Leyden jar.)
In very old sets (those that use a tube for the high voltage rectifier) the CRT
could hold a dangerous charge for weeks! In modern sets, there is enough
leakage back through the HV rectifier diode to drain the charge to a safe level
in "only" a day or two...
The usual procedure for grounding the HV lead is to use a screwdriver with a
long plastic (not wood) handle. Attach a clip lead to the blade shaft and to
chassis ground, hold it by the end of the handle, and gently poke the blade
under the HV connector's "skirt". You will hear a snap as the charge arcs to
the blade. You're not done yet; push on until the blade firmly touches the
connector, and leave it there while you work on the set.
In a similar vein... when working on photoflash units you will find that the
capacitor holds a hefty charge at several hundred volts. After reading the
above, you may be tempted to short the capacitor with a screwdriver blade in
order to avoid a nasty shock. Don't do it! Photoflash capacitors can be
damaged if they're discharged into a dead short. Use a 10K resistor instead.
--- Jamie Hanrahan, Kernel Mode Consulting, San Diego CA