Howdy all..........As it seems there's a lot of fine TV (and other!) techs
on here I thought I'd ask a question thats been bugging me for years. On
my 22+ year old RCA I've noticed for years a faint, approx 2-1/2" wide
horizontal "bar" in the background....just as if the picture was
at-a-different-depth while the bar slowly scrolls up the screen. Picture
isn't otherwise distorted and, most times is not very noticeable. I just
receive off-the-air here......3 signals strong and 2 fringe with the
antenna input usually routed through a VCR. I've tried in the past to
determine whether the bars were interference being received via the power
line or the antenna by selectively disconnecting the VCR and unplugging it
etc......removing and unplugging any active antennas......and finally by
routing the antenna direct to the set (via one 50:300 balun) and tripping
all the circuit breakers in the house except the one supplying the
TV.....and then trying a different circuit for even that. Seeing no
difference......and noting the bars on more than one channel, I've often
thought the problem was likely a distortion in either the horizontal or
vertical retrace circuits......no schematic and I seldom have worked on
TV's in my 30+ years around radio and electronics. This Christmas I bought
a new Toshiba 14AF44 as a second TV for the wife and was surprised to find
the exact same abnomality showing up in it's picture.......no more or no
less than on my old RCA. Trying to figure out a common denominator here
for the problem........I've scoped the house power via a transformer and
don't see any strange features.......I've had dozens of LF, MF, HF, VHF and
up receivers here over the years and have not noticed anything consistent
interference problems......nor noted during the hundreds of hours I've had
my old FM modulation scope on during bench work. Antennas and feedlines
have varied over the years from simple whips and "rabbit ears" to yagis and
dipoles. There is no power company high-lines in our vicinity nor any
industry (I live approx 22 km from the nearest city). There is an ATC
radar site at 4km south......3 TV transmitters and at least one broadcast
FM transmitter 4 - 9 km south of here for consistent "other" signals.


Any ideas on what this might be appreciated.........curiousity has
returned.



Gord

"G" wrote in message
news:01c4eb4f$bb030ea0$45fca68e@ve1ajf...
Howdy all..........As it seems there's a lot of fine TV (and other!) techs
on here I thought I'd ask a question thats been bugging me for years. On
my 22+ year old RCA I've noticed for years a faint, approx 2-1/2" wide
horizontal "bar" in the background....just as if the picture was
at-a-different-depth while the bar slowly scrolls up the screen. Picture
isn't otherwise distorted and, most times is not very noticeable. I just


This sounds like a "hum bar" and is usually caused by dried up electrolytic
capacitors in the power supply.

Hi!

This sounds like a "hum bar" and is usually caused by dried up
electrolytic
capacitors in the power supply.

Yeah, but why on a brand new set? That's the part I find really strange.

William

Could be something related to the supplied signal, power source the devices
are connected to, etc. These types of distortion are only located by one at
a time connecting each item to the set to determine what is causing the
symptom to appear. If it does it only with the DVD connected and is not
visible on the set with only the signal source then it may be hookup or
power source. If it does it only when the source, Be it CATV, Satellite,
OTA, etc then the tele may be suspect but I'd still suspect externally
generated noise. Since it is showing up on two different teles I'd also
suspect highly it being signal source generated. What does the sets look
like with a RF signal generator connected, and via the available AVIO jacks
on the back. Is the bar visible without the source connected while using
only a signal generator?? Need to isolate the devices from the signal source
and check each with a verified signal generator to see if the bar is endemic
in the signal source, such as a defective signal amplifier, ground loop in
the hookup, etc. This kind of fault can be relative difficult to actually
determine the exact source, and then to eliminate it. Good Luck!!
"William R. Walsh" wrote in
message news:xVHzd.566244$wV.352665@attbi_s54...
Hi!

This sounds like a "hum bar" and is usually caused by dried up
electrolytic
capacitors in the power supply.

Yeah, but why on a brand new set? That's the part I find really strange.

William

"James Sweet" bravely wrote to "All" (26 Dec 04 23:32:33)
--- on the heady topic of " TV horizontal bars light in the background?"

JS From: "James Sweet"
JS Xref: aeinews sci.electronics.repair:4809


JS "G" wrote in message
JS news:01c4eb4f$bb030ea0$45fca68e@ve1ajf...
Howdy all..........As it seems there's a lot of fine TV (and other!) techs
on here I thought I'd ask a question thats been bugging me for years. On
my 22+ year old RCA I've noticed for years a faint, approx 2-1/2" wide
horizontal "bar" in the background....just as if the picture was
at-a-different-depth while the bar slowly scrolls up the screen. Picture
isn't otherwise distorted and, most times is not very noticeable. I just


JS This sounds like a "hum bar" and is usually caused by dried up
JS electrolytic capacitors in the power supply.

Parasitic regeneration in the tuner due to dried bypass caps can also
result in hum bars and even though there is very little supply ripple.

A*s*i*m*o*v

.... Reactance: your imaginary friend.

"William R. Walsh" wrote in
message news:xVHzd.566244$wV.352665@attbi_s54...
Hi!

This sounds like a "hum bar" and is usually caused by dried up
electrolytic
capacitors in the power supply.

Yeah, but why on a brand new set? That's the part I find really strange.



Hmm must have misread it, I thought you said it was 22 years old or
something. In that case I dunno.

On Sun, 26 Dec 2004 21:24:29 GMT "G"
wrote:

On
my 22+ year old RCA I've noticed for years a faint, approx 2-1/2" wide
horizontal "bar" in the background....just as if the picture was
at-a-different-depth while the bar slowly scrolls up the screen.

This is the classic "hum bar" pattern. It is 60 cycle noise
superimposed on the picture signal which is just a little under 60
cycles. (That's why it rolls slowly upwards.)

The source of this is either bad filter caps in the set's DC power
supplies, or 60 Hz interference from something else in the
neighborhood.

This Christmas I bought
a new Toshiba 14AF44 as a second TV for the wife and was surprised to find
the exact same abnomality showing up in it's picture.......no more or no
less than on my old RCA.

This makes it almost certain that the problem is radiated 60 Hz
interference, rather than a problem in the older set's DC power
supplies. I'm puzzled by your rather thorough troubleshooting,
however. If I understand correctly, you've already tried turning off
every other electrical item around and the problem persists.

I would extend this test, making sure that you have actually turned
off everything else. You may need to go so far as to turn off compact
fluorescent lamps and unplug items which have standby circuits. Unplug
all wall warts, turn off any lights that work on dimmers, disconnect
dimmers, turn off computer & UPS, etc.

Do you have neighbors hearby? Does this happen at ALL times? I find
that our microwave makes big hum bars in our house.

Once you've made the bars go away, you can turn things back on one at
a time until the bars come back. Then you've found the culprit.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

Thanks all for your input........Jim Adney for reading the post closely and
offering some logical thinking to this.
My selective power-down of the rest of the house was by first unplugging
the couple of wallwarts, UPS on the computer, then anything and everything
else which is why it had me in head scratch mode when the new TV showed the
same symptoms. Your comment on the AC (modulating) the pic causing the
slow roll up makes me wonder whether I've got a ground loop (poor bonding
etc) within the house (can't fathom why this would cause the problem except
for any of these sets being transformerless) or something as odd as
crosstalk from another power phase out at the power pole (or just radiation
from same). Anyway, not bad enough to ruin our viewing worse than the
actual programming but good enough for a wonder-why.


Thanks again all


Gord

On Tue, 28 Dec 2004 02:28:03 GMT "James Sweet"
wrote:


"William R. Walsh" wrote in
message news:xVHzd.566244$wV.352665@attbi_s54...
Hi!

This sounds like a "hum bar" and is usually caused by dried up
electrolytic
capacitors in the power supply.

Yeah, but why on a brand new set? That's the part I find really strange.

Hmm must have misread it, I thought you said it was 22 years old or
something. In that case I dunno.

The original set had the hum bars, and we all thought the reason was
rather obvious, but then the OP mentioned that he had also gone out
and bought a second NEW set, which then displayed the same symptoms.
That's when the problem got interesting.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------