On 08/07/15 09:11, Snuffy "Hub Cap" McKinney wrote:
"whit3rd" wrote in message ...
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.