CRT Television Hum

[Snuffy \"Hub Cap\" McKinn]

I have a analog TV that is still working fine and no plans to replace it. Over time, it has developed an audio hum - I'm guessing it's 60 Hz. When the picture is dark, the hum is nearly gone. The brighter the picture, the louder it is. I'm guessing some kind of filter on the speaker connections would do it, maybe something as simple as connecting a capacitor circuit.... But, as I ain't the sharpest feller with audio electronics, I thought I better ask the genius pool here!

First I thought was a power cord was near the antenna cable, but that doesn't seem to be the problem.

The key word in all this is "cheap". Anything over $10 is way out of line.

Snuffy

 

[whit3rd]

On Tuesday, July 7, 2015 at 12:02:29 PM UTC-7, Snuffy Hub Cap McKinney wrote:
> I have a analog TV that is still working fine and no plans to replace it. Over time, it has developed an audio hum - I'm guessing it's 60 Hz. When the picture is dark, the hum is nearly gone.

Probably the HV flyback power and the audio (sound amplifiers) power are
taken from a common filter capacitor, which has developed high internal resistance.
If you can replace or bypass (put an auxiliary capacitor in parallel with the weak one),
that should fix it.

The hum is caused by voltage droop when the screen is lit, modulated at 60 Hz
because the screen blanks for a while during vertical retrace.

 

[Clifford Heath]

On 08/07/15 09:11, Snuffy "Hub Cap" McKinney wrote:

"whit3rd" <whit3rd@gmail.com> wrote in message news:654d72c9-dfbe-4bb0-b4ec-6a5dc9bd847a@googlegroups.com...
On Tuesday, July 7, 2015 at 12:02:29 PM UTC-7, Snuffy Hub Cap McKinney wrote:
I have a analog TV that is still working fine and no plans to replace it. Over time, it has developed an audio hum - I'm guessing it's 60 Hz. When the picture is dark, the hum is nearly gone.

Probably the HV flyback power and the audio (sound amplifiers) power are
taken from a common filter capacitor, which has developed high internal resistance.
If you can replace or bypass (put an auxiliary capacitor in parallel with the weak one),
that should fix it.

The hum is caused by voltage droop when the screen is lit, modulated at 60 Hz
because the screen blanks for a while during vertical retrace.
Thanks, whit3rd. I would give it a try but unfortunatley for me, I don't have a schematic and not up on TV circuits.

My vote is with this response; it'll be the power supply filter capacitors.

> Not related to this... but have been meaning to ask.... I would like to pick up radio stations AM & FM that have weak signals. Is there a home-brew antenna method I can use for this? Like the TV, if there's something relatively simple and low cost I'd like to try it. Not worth more than a few dollars.

Different solutions for AM and FM. For AM, run a long wire to the
highest point you can. For FM, height matters too, but you need an
antenna that resonates in the right frequency range. So does the use of
good quality coaxial cable. If you can get an old TV balun, hook the 300
ohm side to the inner ends of two 75cm dipole elements, and run the coax
down from that. Orient the dipole broadside to where your transmitters
are. Both are quite easy homebrew jobs.

 

[John-Del]

On Tuesday, July 7, 2015 at 3:02:29 PM UTC-4, Snuffy Hub Cap McKinney wrote:

I have a analog TV that is still working fine and no plans to replace it. Over time, it has developed an audio hum - I'm guessing it's 60 Hz. When the picture is dark, the hum is nearly gone. The brighter the picture, the louder it is. I'm guessing some kind of filter on the speaker connections would do it, maybe something as simple as connecting a capacitor circuit..... But, as I ain't the sharpest feller with audio electronics, I thought I better ask the genius pool here!

First I thought was a power cord was near the antenna cable, but that doesn't seem to be the problem.

The key word in all this is "cheap". Anything over $10 is way out of line.

Snuffy

Are you sure it's coming from the speaker? Deflection yokes are known to hum as the mastic snot that locates the convergence shunts dry up from age.

 

[Snuffy \"Hub Cap\" McKinn]

"John-Del" <ohger1s@aol.com> wrote in message news:5783f073-6dc8-472f-95f3-bf16a8335e9d@googlegroups.com...
On Tuesday, July 7, 2015 at 3:02:29 PM UTC-4, Snuffy Hub Cap McKinney wrote:

I have a analog TV that is still working fine and no plans to replace it. Over time, it has developed an audio hum - I'm guessing it's 60 Hz. When the picture is dark, the hum is nearly gone. The brighter the picture, the louder it is. I'm guessing some kind of filter on the speaker connections would do it, maybe something as simple as connecting a capacitor circuit.... But, as I ain't the sharpest feller with audio electronics, I thought I better ask the genius pool here!

First I thought was a power cord was near the antenna cable, but that doesn't seem to be the problem.

The key word in all this is "cheap". Anything over $10 is way out of line.

Snuffy

- Are you sure it's coming from the speaker? Deflection yokes are known to hum as the mastic snot that locates the convergence shunts dry up from age.

Yes, the hum goes up and down with the volume.

 

[Snuffy \"Hub Cap\" McKinn]

"whit3rd" <whit3rd@gmail.com> wrote in message news:654d72c9-dfbe-4bb0-b4ec-6a5dc9bd847a@googlegroups.com...

On Tuesday, July 7, 2015 at 12:02:29 PM UTC-7, Snuffy Hub Cap McKinney wrote:
I have a analog TV that is still working fine and no plans to replace it. Over time, it has developed an audio hum - I'm guessing it's 60 Hz. When the picture is dark, the hum is nearly gone.

Probably the HV flyback power and the audio (sound amplifiers) power are
taken from a common filter capacitor, which has developed high internal resistance.
If you can replace or bypass (put an auxiliary capacitor in parallel with the weak one),
that should fix it.

The hum is caused by voltage droop when the screen is lit, modulated at 60 Hz
because the screen blanks for a while during vertical retrace.

Thanks, whit3rd. I would give it a try but unfortunatley for me, I don't have a schematic and not up on TV circuits.

Not related to this... but have been meaning to ask.... I would like to pick up radio stations AM & FM that have weak signals. Is there a home-brew antenna method I can use for this? Like the TV, if there's something relatively simple and low cost I'd like to try it. Not worth more than a few dollars.

 

[Dave Platt]

In article <5783f073-6dc8-472f-95f3-bf16a8335e9d@googlegroups.com>,
John-Del <ohger1s@aol.com> wrote:

Are you sure it's coming from the speaker? Deflection yokes are
known to hum as the mastic snot that locates the convergence shunts
dry up from age.

The fact that the hum amplitude changes with brightness, does suggest
to me that the original suggestion is correct. I've heard this sort
of brightness-varying hum from older TVs in the past, and it was
definitely coming from the speakers. TVs are tough places for
capacitors due to the internal heat... so, a dried-up filter cap is a
good suspect.

A lot of "60 Hz" hum or buzz from televisions actually has a lot of
harmonic content - it's a long way from being a pure sinewave. A
simple high-pass or notch filter to take out the 60 Hz won't be very
effective in getting rid of the nuisance.

 

[Chris Jones]

On 08/07/2015 05:02, Snuffy "Hub Cap" McKinney wrote:

I have a analog TV that is still working fine and no plans to replace
it. Over time, it has developed an audio hum - I'm guessing it's 60
Hz. When the picture is dark, the hum is nearly gone. The brighter
the picture, the louder it is. I'm guessing some kind of filter on
the speaker connections would do it, maybe something as simple as
connecting a capacitor circuit.... But, as I ain't the sharpest
feller with audio electronics, I thought I better ask the genius pool
here!

First I thought was a power cord was near the antenna cable, but that
doesn't seem to be the problem.

The key word in all this is "cheap". Anything over $10 is way out of
line.

Snuffy

If you are receiving an analog signal (either from a transmitter or from
a digital converter box) then you may just need to re-check the tuning
to get rid of the hum.

For each channel, the video and sound signals are transmitted on nearby
frequencies, and if the tuning is slightly off, the video signal can get
into the sound receiver, causing a buzz that changes with the picture
content.

If re-tuning doesn't fix it, maybe you can borrow an ESR meter and check
for any dried up capacitors that might be resulting in ripple on a power
supply rail, though I think this is unlikely to affect the sound without
also affecting the picture.

Chris

 

[Tom Miller]

"Dave Platt" <dplatt@coop.radagast.org> wrote in message
news:0i4u6c-kfl.ln1@coop.radagast.org...

In article <5783f073-6dc8-472f-95f3-bf16a8335e9d@googlegroups.com>,
John-Del <ohger1s@aol.com> wrote:

Are you sure it's coming from the speaker? Deflection yokes are
known to hum as the mastic snot that locates the convergence shunts
dry up from age.

The fact that the hum amplitude changes with brightness, does suggest
to me that the original suggestion is correct. I've heard this sort
of brightness-varying hum from older TVs in the past, and it was
definitely coming from the speakers. TVs are tough places for
capacitors due to the internal heat... so, a dried-up filter cap is a
good suspect.

A lot of "60 Hz" hum or buzz from televisions actually has a lot of
harmonic content - it's a long way from being a pure sinewave. A
simple high-pass or notch filter to take out the 60 Hz won't be very
effective in getting rid of the nuisance.


Not only that but it is more likely 120 Hz hum.

 

[John-Del]

On Wednesday, July 8, 2015 at 4:17:40 AM UTC-4, N_Cook wrote:

On 07/07/2015 20:02, Snuffy "Hub Cap" McKinney wrote:
I have a analog TV that is still working fine and no plans to replace it. Over time, it has developed an audio hum - I'm guessing it's 60 Hz. When the picture is dark, the hum is nearly gone. The brighter the picture, the louder it is. I'm guessing some kind of filter on the speaker connections would do it, maybe something as simple as connecting a capacitor circuit.... But, as I ain't the sharpest feller with audio electronics, I thought I better ask the genius pool here!

First I thought was a power cord was near the antenna cable, but that doesn't seem to be the problem.

The key word in all this is "cheap". Anything over $10 is way out of line.

Snuffy


I would go with loose frame-deflection yoke coil, wash over with
traditional copal varnish and allow to dry.

Although a common problem, OP responded that the noise tracks with the volume, so that leaves out mechanical considerations.

 

[N_Cook]

On 07/07/2015 20:02, Snuffy "Hub Cap" McKinney wrote:

I have a analog TV that is still working fine and no plans to replace it. Over time, it has developed an audio hum - I'm guessing it's 60 Hz. When the picture is dark, the hum is nearly gone. The brighter the picture, the louder it is. I'm guessing some kind of filter on the speaker connections would do it, maybe something as simple as connecting a capacitor circuit.... But, as I ain't the sharpest feller with audio electronics, I thought I better ask the genius pool here!

First I thought was a power cord was near the antenna cable, but that doesn't seem to be the problem.

The key word in all this is "cheap". Anything over $10 is way out of line.

Snuffy

I would go with loose frame-deflection yoke coil, wash over with
traditional copal varnish and allow to dry.

 

[Mark Zacharias]

"John-Del" <ohger1s@aol.com> wrote in message
news:4ec26c55-28b1-474a-b1b5-bf12c40fecc6@googlegroups.com...
On Wednesday, July 8, 2015 at 4:17:40 AM UTC-4, N_Cook wrote:

On 07/07/2015 20:02, Snuffy "Hub Cap" McKinney wrote:
I have a analog TV that is still working fine and no plans to replace
it. Over time, it has developed an audio hum - I'm guessing it's 60 Hz.
When the picture is dark, the hum is nearly gone. The brighter the
picture, the louder it is. I'm guessing some kind of filter on the
speaker connections would do it, maybe something as simple as connecting
a capacitor circuit.... But, as I ain't the sharpest feller with audio
electronics, I thought I better ask the genius pool here!

First I thought was a power cord was near the antenna cable, but that
doesn't seem to be the problem.

The key word in all this is "cheap". Anything over $10 is way out of
line.

Snuffy


I would go with loose frame-deflection yoke coil, wash over with
traditional copal varnish and allow to dry.

AGC problems can cause video to bleed over into the audio circuits.

Mark Z.

 

[Jeroni Paul]

Snuffy Hub Cap McKinney wrote:
> I have a analog TV that is still working fine and no plans to replace it. Over time, it has developed an audio hum - I'm guessing it's 60 Hz. When the picture is dark, the hum is nearly gone. The brighter the picture, the louder it is.

If you are tuning analog signals on VHF/UHF recheck the fine tuning, the tuner could have drifted slighty over time. If it has AFC try to disable that and fine tune manually.

The cheap scart plugs common around here tend to make poor contact and cause these problems. Usually the problem is fixed by reseating the plug. Either the pins develop some type of corrosion or contact resistance or the small wires that are pressure pressed inside the plug are not very well pressed..

 

[Snuffy \"Hub Cap\" McKinn]

"Snuffy "Hub Cap" McKinney" <Snuffy-Hub-Cap@Livebait-McKinney.com> wrote in message news:hI6dneJjLo7dvwHInZ2dnUU7-TmdnZ2d@earthlink.com...
I have a analog TV that is still working fine and no plans to replace it. Over time, it has developed an audio hum - I'm guessing it's 60 Hz. When the picture is dark, the hum is nearly gone. The brighter the picture, the louder it is. I'm guessing some kind of filter on the speaker connections would do it, maybe something as simple as connecting a capacitor circuit.... But, as I ain't the sharpest feller with audio electronics, I thought I better ask the genius pool here!

First I thought was a power cord was near the antenna cable, but that doesn't seem to be the problem.

The key word in all this is "cheap". Anything over $10 is way out of line.

Snuffy

==
Thanks for all the good info. If I had a place to work, I would take a look, but the most practical for this one is to get a replacement set, new or used.

I use a CRT monitor on one of the computers here and LCD displays can't compare with his colors. But the power cost is definitely higher -- plus, more importantly during the summer - it heats up the room...

 

[Jeroni Paul]

CRTs are better as they generate the required light only, unlike LCD where the backlight is always full on no matter the screen contents. This is an advantage as far as efficiency goes. Also LCD require more digital processing. At the end the energy wasted to run both is similar, just look at the rated power consumption, you may be surprised. 28" CRT TVs take 100W typ. while similar size LCD are rated 130W typ.

 

[Jeroni Paul]

CRTs are better as far as efficiency goes in they generate the required light only, unlike LCD where the backlight is always full on no matter the screen contents. Also LCD require more digital processing. At the end the energy wasted to run both is similar, just look at the rated power consumption, you may be surprised. 28" CRT TVs take 100W typ. while similar size LCD are rated 130W typ.

 

[Jeroni Paul]

CRTs are better as far as efficiency goes in they generate the required light only, unlike LCD where the backlight is always full on no matter the screen contents. Also LCD require more digital processing. At the end the energy wasted to run both is similar, just look at the rated power consumption, you may be surprised. 28" CRT TVs take 100W typ. while similar size LCD are rated 130W typ.

 

[Ralph Mowery]

"Snuffy "Hub Cap" McKinney" <Snuffy-Hub-Cap@Livebait-McKinney.com> wrote in
message news:hI6dneJjLo7dvwHInZ2dnUU7-TmdnZ2d@earthlink.com...

I have a analog TV that is still working fine and no plans to replace it.
Over time, it has developed an audio >hum - I'm guessing it's 60 Hz. When
the picture is dark, the hum is nearly gone. The brighter the picture, the
louder it is. I'm guessing some kind of filter on the speaker connections
would do it, maybe something as simple >as connecting a capacitor
circuit.... But, as I ain't the sharpest feller with audio electronics, I
thought I better ask >the genius pool here!

First I thought was a power cord was near the antenna cable, but that
doesn't seem to be the problem.

The key word in all this is "cheap". Anything over $10 is way out of line.

Look on Facebook or Craigs list for a free TV. They are always giving those
old things away.
The power cord could be wrapped around the antenna and not cause hum.
Probably a filter capacitor needs replacing. If you had some on hand, open
the TV up and just hold the leads of the new one across the capacitors and
find the one where the hum quits .

 

[Chris Jones]

On 16/07/2015 01:57, Jeroni Paul wrote:

CRTs are better as far as efficiency goes in they generate the
required light only,

Though I guess at least 2/3 of the electron beam power in a CRT would go
into heating the shadow mask or aperture grille. (Unless it is a black
and white set.)

unlike LCD where the backlight is always full on
no matter the screen contents.

As well as the picture content, I guess in LCD TVs they lose a lot of
light in the polarisers, on top of what is lost in the R,G,B filters.

Also LCD require more digital
processing. At the end the energy wasted to run both is similar, just
look at the rated power consumption, you may be surprised. 28" CRT
TVs take 100W typ. while similar size LCD are rated 130W typ.

You make a good point, some CRT TVs are quite efficient. Also I like the
idea of having a particle accelerator in the living room.

 

[MJC]

In article <55a7a649$0$12482$862e30e2@ngroups.net>, lugnut808
@spam.yahoo.com says...

You make a good point, some CRT TVs are quite efficient. Also I like
the idea of having a particle accelerator in the living room.

You've probably got one in the kitchen, too!