OT tv on off switch

[Anonymous-0]

have a tv that goes off on its own can be turned back on either manualy or by remote . don't last long and goes off again . any ideas ?

 

[sd farm boy]

Buy a new tv. The cost to repair it, if you can find someone to repair it anymore, will be as much or more than a new one.

Anyway not to get too technical, its not as simple as an on/off switch anymore. Some TV's monitor some signal componets and if the signal componets or TV circuity are are out of spec, the TV will turn off.

 

[Allan in NE]

Mornin' Bill,

It's not popping the reset either. Right?

Just going off on it's own for no apparent reason? Sometimes it will run okay for hours and then again at other times it does it repeatedly in short order?

Allan

 

[Anonymous-0]

Try using the manual control only and take the batteries out of the remote to see if the remote control is the problem.

 

[Anonymous-0]

yes you have pretty much described it . just turns off on it's own . no set amount of time for turn off .

 

[Anonymous-0]

have already replaced it . would like to repair it for my grandson . suspect it is something like a transistor that is operated by the remote and manual switch . part can probably be gotten at radio shack if i can identify it . will not go to a repair shop .

 

[supergrumpy]

I have heard plenty of warnings about high voltage inside a TV, flyback transformer seems to be the rattlesnake hiding in there

please be careful

 

[Allan in NE]

Bill,

Just about bet you live in a rural area?

Don't think the problem is the TV at all. Really sounds like a line voltage fluctuation thing. On peak demand times, I’ve seen spikes in the area of 135-140 volts AC.

Good TVs will have a clamping regulator built into it's power supply to protect itself from this phenomena. Shuts itself down if the incoming power is too high or too low.

You can get around this problem by buying a simple line voltage regulator at radio shack and plugging the TV in to it; will probably run in the area of $40 or so?

Now, if you do in fact live rural and want to test this theory; just take the unit into town and see if it still does it there. Urban utilities/power are more often regulated closer. Or otherwise, simply measure and monitor the voltage at your outlets.

The first time I ran into that head-scratcher, it about drove me nuts!

Good luck,

Allan

 

[Allan in NE]

Yeah But,

After reading the discussion on the tractor talk yesterday morning, I'm to believe that in some circles rattlesnakes are considered a good thing? :>)

Allan

 

[Bill in IL]

Do you have any flourescent lights in the room with your TV? I have hear of problems with them giving off infrared radiation and mimicking your remote causing changing channels and on off situations.

 

[randy47]

Probably GOD tellin ya to get off yer butt!!!!!

 

[Bob]

(In a "past life", before throwaway TV's, I was a TV repairman, certified by a couple of brands.)

There is a circuit that senses the (approx. 30KV) voltage aplied to the picture tube anode, using a voltage divider to feed a reduced voltage (pulses) to the monitoring circuit.

If the HV IS exceeding design limits, the circuit "kills" the HORIZ oscillator circuit, effectively shutting down the TV 'till it's shut off, and the circuit rests. ("X" rays can be produced if the CRT's andode voltage exceeds safe limits.)

So, the first scenario is that the safety shutdown circuit is behaving properly, and there's a power supply regulation problem. Too much B+ voltage (typically runs around 130 volts), and there will be too much HV, and the safety circuit will kick in, shutting the set down.

The other scenario is that the safety shutdown circuit itself has gotten a bit of a "hair trigger" attitude with age, and is needlessly shutting down the set.

EITHER scenario is commonly caused by an electrolytic capacitor that has either become "open" or "leaky". (OBVIOUSLY, there can be MANY different causes for this behavior BESIDES one or more 'lytics.)

Figuring out WHICH of the dozens of 'lytics that MAY be going bad requires a service manual (at the very least, a schematic), and some knowledge of working on the innard of a TV without getting zapped by the 120 VAC "live chassis" parts, the B+ power supply section, and the HV section. Oh, yeah, and an "isolation transformer".

DON'T mess around in there, unless you have the safety knowledge, a service manual, and an isolation tranformer.

 

[Anonymous-0]

That's a Good One ---- wonder if he took notice !!!!

 

[Anonymous-0]

Don't know if you have been in a RS store lately but they have not much more than a couple of radio controlled race cars and some cellular phones. I you need parts better to try Ellectonixonline or All Electronics. Just repaired a Klipsch computer speaker system and all it needed were two HEXFETS. Finding the parts was the majority of the task.

 

[Aaron Ford]

Be careful, or you might touch the back of the tube and have a hole in your finger that you could run .032 safety wire through. Ask me how I know....

My brothers TV does the same thing..... Haven't looked into that one yet.


Aaron

 

[KEB1]

Unless its really old, all the electronics are on one non-repairable circuit board. The days of TV's with discrete components, whether transistors or tubes, are long gone. I repaired TV's in high school 35+ years ago, and even then the manufacturers were starting to migrate to single board configurations where all you could do was replace the board. Plus, even if you could figure out a bad component, you'd likely need specialized soldering equipment to replace it.

Cheap to manufacture often equals non-repairable.

Keith

 

[Bob]

The CRT, which s just like a BIB Leyden jar, is what REALLY packs the bite!

 

[Anonymous-0]

I gave up TV repair 10 years ago.The safety shut down circuits cause plenty of problems.Over voltage would cause arcing around the anode would put cracks in the glass of the pix tube.If some of these wanna be TV techs ever see a 25 to 30000 volt arc they will leave the tv alone.One fellow brought in an old Raytheon tv chassis that he was trying to fix.This tv had no doghouse over the 1B3.I had just plugged it in when he said I wonder if I put that cap on tight.Before I could say dont he tried to put his finger on the 1B3 cap.The purple arc jumped at his finger.Made him change his mind fast.He had tested all the tubes in a drug store tester.The pix tube heater was out,I got out the crimp tool and crimped the heater pins.There were two weak tubes that had to be replaced.A hand to hand shock from a charged pix tube could be dangerous, it could send your heart to racing out of control.Hi volt arcs can cause deep burns that are hard to heal.