the screen on sony tv (27" 15 years old) going dark?

Question

when you turn the tv on...it works for about 10-15 min then slowly goes dark with just a little picture showing around the edges of the screen. If you then turn it off, then on, it works fine for about 3-4 minutes then goes slowly dark again (takes about 15 seconds to go dark. How do I check to see what it wrong? thanks....roger

Answer 1

Usually when your tv screen fades SLOWLY away as you described there is a problem in the filament circuit. This is the low voltage circuit which lights your picture tube as opposed to the high voltage circuit. This is supplied by the flyback transformer & goes up to the tube socket.
Normally it's just a bad connection either on the main printed circuit board or the tube socket pc board & only requires resoldering.
If you look down through the back of the cabinet of the set, while it is working fine you should see the neck of the tube lit.
Once your problem occurs you won't see any light at all.

Answer 2

What is happening in your set is as the tube heats up the elements expand and the internal short gets connected. The brightness then goes away because of the short.

A new tube is not worth it, but often the tube can be rejuvenated by burning out carbon buildup between the electrodes.

It takes a special test box and a tech who know what they are doing. Depending on the cost, it may be worth it. It is NOT guaranteed to last for any particular length of time - so it is a gamble. I've seen them last for years and weeks.

NOW, if you are handy and want to experiment, you can find a transformer outputting 700V or better (a very old TV power transformer) and connect it across the pins of the tube. First, you need to get the specs of the tube or trace wires cause you don't want to put that voltage on the heaters. Across any other pins is ok. Most likely it is heater to cathode. But try others first as that one has the greatest likelyhood of frying the tube heater.

My tech once used the 25,000 volt anode voltage of a tv to clear a stubborn short in the set. NOT RECOMMENDED.

You might have to try an oil furnace ignition transformer or a neon sign transformer, but those are 5000 to 15000 volts. Just be aware and don't fry the carbon from between your ears. A Variac would help to control the voltage.

good luck.

Answer 3

You have what is called a thermal problem. Something is overheating and when it over heats the TV stops working.

Do you live in the United States? It is time to get a new TV anyway. The US stops broadcasting in analog on February 17, 2009 (last date of current service). Unless you have cable or satellite you will need a converter or a new TV. Details available at http://www.dtv.gov

A 15 year old TV is pretty old, in other words, you did get the expected life out of it. If you still want to keep this TV take it to someone who is trained it its proper service. The most likely problems are in the high voltage sections of the TV and that is the kind of problem that the average person should leave alone for his or her own safety.

Answer 4

Your parents are wrong. Yes, it's normal. I'm afraid of the dark and feel like I see things moving around on the ceiling when the lights are off. And I'm 7 years older than you. As for overcoming the fear, I have no clue. You could probably get some hypno-therapy or maybe research self-hypnosis.

Answer 5

Loose solder on the CRT picture board....OR the Heater

Answer 6

looks like the pixel tube is dying.

if it lasted for 15 years, that's long enough.

time to get a new HDTV.

(it will cost about $600-700 to get a new tube and that's not worth it for a CRT. you could get a 32 inch LCD HDTV for $500 now)

Answer 7

I'm assuming its a crt television so that probably means it needs a bulb-replacement soon. I could be wrong so you should probably have a chat with any tv specialist in your area about the possible problems with your set. hope i could help.

Answer 8

its not the tv, its your eyes, they are getting tired of watching tv.