I have an 8 or 9 year old Magnavox television that has a very
conditional problem. During the daytime, the picture is great, but when
it is dark outside, not just dark inside, the picture gets interferance
in the top 1/3 of the screen, in the shape of a thick black line that is
shaped like an arrowhead, that jumps from the left side of the screen to
the right. Anyone have a theory?
Just a couple of wild-ass guesses, but here goes...
1. A change in line voltage after sunset. Does the same thing happen if
you plug the set into a receptacle that's on a different circuit?
2. If you're on cable, could it be a problem with your cable service
I had a similar problem on my SONY that I couldn't recreate. The
only clue was it sometimes crapped when the forced air furnace came on
thus indicating it had something to do with external temperature.
I had taken some night courses on TV repair and tried many times over
3 to 4 years to locate the problem without success. There wasn't much
to look at anyway because everything was on one PCB and the parts were
unidentifiably teeny. The set was very compactly assembled as to be
barely reachable with any tool. If I couldn't reproduce the problem
and couldn't locate the circuitry area I wasn't about to bring that
hernia box to the repair shop because they would likely encounter the
On the final try I got lucky. My hand brushed the cable harness to
the CRT display tube and that reproduced the problem. A close look at
the harness connector pins on the PCB revealed hairline cracks on the
solder pads. I resoldered the pin pads and my TV set image is now
clearer and sharper than it had ever been.
For your repair attempt open up the cover. Use a wooden dowel to
jiggle all the wire harness connections to see if you can reproduce
the problem. It may be the same problem and have the same solution as
mine. Beyond that don't spend any more time and money on repairing an
old TV set. Its cheaper to buy a new one. Or you can live with your
I saw a problem like this once at a vacation cottage on Cape Cod.
In the evenings a powerful radar system was turned on probably by the coast guard
or military which made a mess of the TV picture.
Depending on where he lives there are alot of Military Ultra high
powered long range comuniction equipment around. He should talk to
neighbors , see if any have problems or run apliances at night. I
dought it could be a refrigerator defrost cycle , its a coil. Ive had
CB radios come in my tv from 1 mile away.
My guess is some lighting, interior or exterior, maybe even street
lighting near your home or more likely near the cable line, is causing
interference. Can you reproduce it with a second TV set? Newer sets may be
more resistant to the interference. You might also ask your neighbors if
they are having a like problem.
Call your cable company (I suspect it is cable) and have them check
their cable lines run on the same poles as street lights and I'll bet if
they look they will find one of their amplifiers is on the same pole as a
light with a defective ballast.
Its something that turns on at night, and inducing RF or line
interference. As Joe sais maybe street lights. Time the lights, have tv
on , wait for the lights. Or something else that turns on at night. A
neighbors air filter , AC, fan , or something. Try a different
circuit . Maybe a Ham radio, or CB radio, operator in the area, look
for a big antenna , See what time it goes on and off. A radio operator
will have a sleep time he leaves. street lights have an exact time.
call your cable co they will have better ideas, but talk to a Tek, not
sales. Unlikely but a frige has a defrost cycle. I say Radio operator.
Questions to ask:
Is this pattern visible on one station or all stations?
Does the pattern crawl up or down the screen?
Is anyone else in the area having similar problems?
Can you change the pattern by bumping the set? On a healthy set you
should be able to wack it with the flat of your hand without any visual
or audible problems. (As long as you don't cause any physical damage to
the cabinet, controls, or your hand, hit it as hard as you can. Sets
are not particularly fragile.) Be sure to hit in all directions.
Is the set sensitive to jiggling any of the connecting wires?
If you have other TV sets in the area, do they have any similar
Are you keeping a written log of problems? If so, can you correlate TV
problems with anything? You mentioned time of day. What about weather,
day of week, other appliances in the area, computer use, video games,
power tools. Look outside; what is happening out there?
Did anything in the area change at about the same time as the problem
started? (construction, new neighbor, utility crew working in the area)
wordgame:123(abc):<14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
13> (Barry Mann)
[sorry about the puzzle, spammers are ruining my mailbox]
Do you have another TV? If not, borrow one and see if it does it too.
Do you have a VCR or DVD? try to play a disk or a tape without the
antenna connected and see if it still does it.
Is the picture full and squished and the stuff on the top of the screen
just garbage? If so, you have a vertical problem. More than likely bad
capacitors. You really need to know what your doing to work on a TV.
THe CRT is really just a big capacitor that can store 25,000 volts
or so. SO careful is the word.
Worse on one channel than on others, right?
You're picking up another station on the same channel from a distant
station, at the same time you're getting the local channel. The "thick
black line" is the horizontal blanking bar from the distant station.
Rather than "jumping" from one side to the other, I bet it floats
gradually from one side to the other, then appears at the one side
again to start over.
You *may* be able to turn your antenna a little to alleviate this,
but that might cause other problems. You'll probably want to get an
attenuator, but what type depends on whether you're using coax or
flat twinlead, and how much attenuation has to be determined by some
experimentation. Electronics parts jobbers who sell to TV shops, or
stores that are really good with antennas, should have them.
Just on the off chance that you're using an antenna amplifier with
a strength control, try turning that down. (Few have them.)
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