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  #1  
Old 10-15-2014, 11:24 AM
idiotbox idiotbox is offline
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Exclamation How to Stop High-Pitched Humming from 70s TV's?

I've got a couple B&W TV's from the 1970s that as soon as I turn them on, emit a painfully high pitched and loud hum. They are a 1975 Quasar and a JVC Model 3240 Videosphere. Is this normal and is there anything I can do to stop/reduce the hum? I have the ears of a dog so maybe others haven't noticed this. It's gotten to the point where I can't be in the same room as the TVs because it is so uncomfortable (which really takes the fun out of putting them to use). I have no clue what exactly causes the hum, but even with the volume all the way down the hum doesn't change. Thanks in advance.
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  #2  
Old 10-15-2014, 11:42 AM
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NoPegs NoPegs is offline
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Quote:
Originally Posted by idiotbox View Post
I've got a couple B&W TV's from the 1970s that as soon as I turn them on, emit a painfully high pitched and loud hum. They are a 1975 Quasar and a JVC Model 3240 Videosphere. Is this normal and is there anything I can do to stop/reduce the hum? I have the ears of a dog so maybe others haven't noticed this. It's gotten to the point where I can't be in the same room as the TVs because it is so uncomfortable (which really takes the fun out of putting them to use). I have no clue what exactly causes the hum, but even with the volume all the way down the hum doesn't change. Thanks in advance.
It is the 15.734 kHz horizontal sweep rate inherent in NTSC displays. I share your pain. In grade school I could hear a TV left on from 3 rooms down the hall with the doors open. Even as an adult my hearing still goes up around 17kHz according to the last occupational hearing evaluation I had in 2012.

Or are you experiencing a low frequency hum in the audio circuit? That can usually be fixed, unlike the 15.734 kHz whine.
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  #3  
Old 10-15-2014, 02:21 PM
idiotbox idiotbox is offline
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Originally Posted by NoPegs View Post
It is the 15.734 kHz horizontal sweep rate inherent in NTSC displays. I share your pain. In grade school I could hear a TV left on from 3 rooms down the hall with the doors open. Even as an adult my hearing still goes up around 17kHz according to the last occupational hearing evaluation I had in 2012.

Or are you experiencing a low frequency hum in the audio circuit? That can usually be fixed, unlike the 15.734 kHz whine.
Hi NoPegs. No, it's the high frequency hum. My question is if it's all NTSC displays, how come there are some TVs that don't emit this hum?

And how do you watch your vintage TVs without getting a splitting headache!?!
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Old 10-15-2014, 02:53 PM
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zenith2134 zenith2134 is offline
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It is dependent on horizontal and high voltage design. What materials they used in the flyback case, the insulation type on the 2nd anode wire, the hv rectification diode(s), and ultor voltage level. Sometimes, the focus block can emit the highest whine of the whole system. In my experience, some G.E.s from the 70s were the loudest; at least one I owned had secondary harmonic content along with the usual 15.7kc tone.
As for quieting them down, I suppose you could try tightening the bolts on the TO-3 cased horiz output, reflowing all solder joints under the fly, and maybe even applying some voltage-suitable silicone agent around the hv section. At your own risk.
Me, I am not bothered by the sound.
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  #5  
Old 10-15-2014, 04:35 PM
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Those sets are new enough they probably have Molded Epoxy Flybacks so they're not as likely to be noisy, the yoke could be singing, that could be tightened possibly but most likely it's just the way they are and nothing will shut them up.

You don't say how old your are but younger people can usually hear high frequencies better.

I'm 55 and can still hear a horizontal oscillator, it's the vocal ranges I have trouble with.
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  #6  
Old 10-15-2014, 05:31 PM
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zeno zeno is offline
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Its caused by a mechanical vibration.
First probe around the HV area to see if your noise
goes away. You can also make a stethoscope out of an
old paper towel tube or the like to pin point it.
If the flyback has nuts on it usually a very slight tightening
will fix it. Dont tighten much or you will crack the core.
Also check it mechanically such as screws holding it to
the PCB or frame. If its between the PCB & FBT wedge it.
If you can push & make it go away you can also wedge it often.
Same deal with yokes but its almost always the FBT doing it on
a B&W. Once in a while it will be a hefty coil in the yoke ckt
vibrating.

On a color set you can add the pin ckt & switching power supplys
to the list of suspects..........

In any case all sets do it some worse than others. I cant hear it
unless its really bad. Thats what happens when you put a box
of rounds through a .44 magnum without ear plugs

73 Zeno
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Old 10-15-2014, 06:48 PM
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Quote:
Originally Posted by zeno View Post
In any case all sets do it some worse than others. I cant hear it
unless its really bad. Thats what happens when you put a box
of rounds through a .44 magnum without ear plugs

73 Zeno
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  #8  
Old 10-15-2014, 07:19 PM
Gunslinger Gunslinger is offline
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Try placing wooden tooth picks at the transformer cores, applying RTV on ferrite beads on component legs. Repack Heat sinks with proper grease compound.
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  #9  
Old 10-15-2014, 11:06 PM
idiotbox idiotbox is offline
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Im in my 20s. You guys are talking over my head as I have no experience in electronics. I think I'll have to take them to someone who knows what they're doing.
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  #10  
Old 10-16-2014, 08:40 AM
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NoPegs NoPegs is offline
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Quote:
Originally Posted by idiotbox View Post
Im in my 20s. You guys are talking over my head as I have no experience in electronics. I think I'll have to take them to someone who knows what they're doing.
Youth is no excuse!

I turned 29 this year(For the first time) and you're making me feel old already.


However, you do show good judgement in knowing when a task is beyond your capability and should seek assistance. Maybe society has a chance after all...


We're all more or less used to two kinds of new member questions: Either someone inherited some vintage gear and wants advice on if it has value or if anyone here would give it a good home, or they're someone who does electronics, and seeks advice on their issue(s). I took you for the second type, as did a few others it seems.
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  #11  
Old 11-02-2014, 06:43 PM
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I can hear horizontal frequency but am usually not bothered by it. Only exception was a Y2K era sharp that I used to own...I could hear it from a tremendous distance, given the house we lived in when I used it ate sound, and while I could put up with it there were a few times I wanted to smack it.
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  #12  
Old 11-03-2014, 07:50 AM
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The old shop I worked at had some sort of spray for quieting noisy yokes. Would penetrate the windings and dry. Probably not much more than a clear coat with an enamel-safe solvent.

OR listen to enough loud music and go to lots of concerts over a 20 year period with no ear protection, give yourself tinnitus, and that 15,734 Hz horiz sweep noise will be drowned out by the internal ringing in your head! I know all about that, Used to be able to hear up to 22k....


EDIT: Looks like one brand of that spray was GC Electronics #10-8665.

Last edited by Ed in Tx; 11-04-2014 at 10:23 AM.
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  #13  
Old 11-03-2014, 01:30 PM
DaveWM DaveWM is offline
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one zz top concert at the hollywood sportatorium cured me of that pesky problem, now I hear it all the time regardless if any tv is on.
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  #14  
Old 11-03-2014, 03:04 PM
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Findm-Keepm Findm-Keepm is offline
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Originally Posted by DaveWM View Post
one zz top concert at the hollywood sportatorium cured me of that pesky problem, now I hear it all the time regardless if any tv is on.
...or one F/A-18C doing a low power turn in hangar bay two - same effect, no marijuana smoke.....
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