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TV sounds like dripping faucet when off

This might not be directly related to design, although possibly the original design of the TV, so here goes..

I have a fairly old (maybe 1990) Emerson color TV which has worked fine for all that time. A few days ago, I heard a sound that was just like a dripping faucet, at about a one second repetition rate. I traced it to the TV, and it seemed to be coming from the speaker. I unplugged it, because I have heard of some TVs catching fire when their standby circuits malfunctioned. It seemed OK later when I reapplied power, but the problem returned some time after I turned it off.

The TV may have been damaged by the close lightning strike that I described in early July. I also noticed soon after that happened, that there is a streak in the center of the screen that shows an abnormally red color.

It's probably not worth taking apart and doing extensive troubleshooting, but I just wanted to know if anyone has experienced anything like this, and what it might be. It acts like a buildup of charge and then a sudden discharge, but I would think the only thing powered up when it is off is the remote control IR detector circuit. The power on circuit might trigger a triac that could be leaky, but I hear a distinct click when the TV turns on, indicating a relay.

I need to move the TV soon to do some remodeling. Maybe I'll take it apart and see if there's anything obvious. Otherwise, maybe it would be safer to just get a new TV for $200 or so. Meanwhile, I'll keep it unplugged while not watching it.

Paul

Reply to
Paul E. Schoen
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(1) Take the back off and thoroughly vacuum the dust out of it (while unplugged of course ;-)

(2) Power it up, then degauss the screen.

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
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Reply to
Jim Thompson

Obviously a drain problem on a field effect transistor.

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Reply to
Don Lancaster

Sno-o-o-o-ort ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.
Reply to
Jim Thompson

On a Magnavox set I recently dug into, the primary switching power supply is always hot. There is 130 Vdc to the HV flyback primary. Turning the set 'on' enables its switching circuitry and the tuner and audio systems. The only relay in that set powers the degaussing coil.

distinct click

It could be a primary power relay, or the degaussing supply. But there is enough stuff energized in a set that is off to cause a bad component or dirty trace to flash over periodically.

Not a bad idea. In my experience, when the bad component finally goes bang, if you are there to unplug it and prevent further damage, it makes the diagnostic process a lot simpler. Just look for burnt stuff.

--
Paul Hovnanian     mailto:Paul@Hovnanian.com
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Reply to
Paul Hovnanian P.E.

Try news:sci.electronics.repair . Give them the Brand and Model numbers, as well as the symptoms and they may be able to help you.

It sounds like some failing electrolytics in the switching power supply.

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Michael A. Terrell
Central Florida
Reply to
Michael A. Terrell

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

If this were a much older model, especially one made in the UK, I would suspect a leaky valve!

(Thanks for the suggestions, BTW)

Paul

Reply to
Paul E. Schoen

Could be the power supply electrolytics running dry (literally, the electrolytic cooks away slowly over time):

In standby the power supply deliberately runs in a burst mode swithing On for a few msec every few seconds- mainly because the regulator in the 150W(???) does not control that low (5W ???) but it *does* conserve some power. If the output capacitors are weak, the supply voltage will vary quite a bit which might feed over to the audio circuits. In normal use the power supply performs glossing over the problem.

Sensible - TV's *like* to catch fire; like tumble-driers.

If you are really devious, you remodel *after* the TV catches fire ....

Reply to
Frithiof Andreas Jensen

Could be a leaking tap on a transformer or coil. I would think a drain problem would cause increasing gurgling/sloshing sounds or puddles of electrons near the device.

Reply to
xray

It was the lightning. You can fix it, if you're good with TVs. I once was sitting in my apartment, watching TV, and the building took a direct strike. It killed the answering machine, so luckily the modem was unplugged, and the TV acted normal, until I went to turn it off and it wouldn't turn off. Turned out it was the "turn it on or off by the remote" transistor, like a 2N3904, had gone short. Cost me $30.00 to get it diagnosed, and a spare transistor and a few minutes to fix it. :-)

Lightning does strange things, and it sounds like your circuit has been mysteriously altered, such that you have a relaxation oscillator somewhere in there.

Like I said, you can fix it, if you have the schematic and all the voltage and signal specs, a scope or so, and etc., but you have to be OK with fixing TVs. :-)

Good Luck! Rich

Reply to
Rich Grise

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