I have a older TV, 98, and the picture goes very dark after it has been on for about a min or two. Adjusting the brightness does nothing, thing acts like it is set permently on dark. Is it possible to replace a part to fix it? I had a friend who did his own repair for vertical hold that was FUBAR on his set, just trying to get an idea if I might be able to do something on my own.
So is there anything I can do to fix my brightness problem on this set?

Find the service manual for your model of set and check it out,there may be parts you can replace easily to fix it. Barring that Wal-Mart has flat panels on sale.

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1988 Fiero Formula T-tops
CJB 143 of 1252 "factory T-top cars"

not much experience - just going by what I know of how a TV works - I am guessing the power to the electron guns is failing.

quote Originally posted by Pyrthian: not much experience - just going by what I know of how a TV works - I am guessing the power to the electron guns is failing.

Anything that can be replaced to fix that other than a new TV? Got a lot of gameing and DVD use out of this thing, just hate to let it go without a try at fixing it. One of the reasons I buy a junker car that should have been destined for the scrap yard and drive the thing for 10 years. Ya I know, but being cheap has served me well over the years, I only junk things when there is nothing more to do, or safety becomes an issue, ONLY two reason I ever got rid of anything.

If it is a Zenith, forget it, it is most likely the Pix tube.

Bang on the set while it is on (and in the failing mode) several times in different spots with your fist. Does it try to get bright again?

quote Originally posted by OH10fiero: Anything that can be replaced to fix that other than a new TV? Got a lot of gameing and DVD use out of this thing, just hate to let it go without a try at fixing it. One of the reasons I buy a junker car that should have been destined for the scrap yard and drive the thing for 10 years. Ya I know, but being cheap has served me well over the years, I only junk things when there is nothing more to do, or safety becomes an issue, ONLY two reason I ever got rid of anything.

I dunno. hard to say. start by the obvious open it up, and looking for obvious signs of damage - burn spots on the boards, and swollen capacitors, blown fuses. a swollen capacitor looks much like a coke can thats been left in the freezer. the tops bowed out, sometimes the case itself gets barrel shaped. next, if you dont find anything - since your failure seems to happen quickly, as it powering up - it maybe heat related. get a can of compressed air, and hit transistors & IC's one at a time with the air to cool them. if you hit one, and your pic comes back - guess what you just found?

but, anyways - no I have no specific info - just general troubleshooting.....

I don't know much about TV repair, other than except for very expensive sets, it usually cheaper to buy a new one than to have an old one repaired.

And be very careful if you decide to open the case. Picture tubes can hold a lethal amount of ZAP!!! even when the TV is unplugged.

quote Originally posted by GT86: I don't know much about TV repair, other than except for very expensive sets, it usually cheaper to buy a new one than to have an old one repaired. And be very careful if you decide to open the case. Picture tubes can hold a lethal amount of ZAP!!! even when the TV is unplugged.

actually - its the capacitors that hold the ZAP. the tube may have so built up static - but they've added a cable to the tube in the late 70's to discharge static from the tube. in fact - failure of this cable can in fact cause this guys problem.

edit - the cable looks like a spark plug cable attched usually on the top with what looks like a suction cup.

[This message has been edited by Pyrthian (edited 12-05-2007).]

You are correct, it's the capacitors that hold the charge. I meant to say that the inside of a set can be dangerous, for some reason it came out as picture tube

[This message has been edited by GT86 (edited 12-05-2007).]

quote Originally posted by Pyrthian: actually - its the capacitors that hold the ZAP. the tube may have so built up static - but they've added a cable to the tube in the late 70's to discharge static from the tube. in fact - failure of this cable can in fact cause this guys problem. edit - the cable looks like a spark plug cable attched usually on the top with what looks like a suction cup.

OK, lets try to get this straight.

I have worked on televisions for 30+ years. Believe me, CRT picture tubes can hold a charge. There is no "cable" in any CRT set (new or old) that I know of that discharges CRT's.

You can manually discharge a CRT but you should know what you are doing before attempting it.

The cable (usually red in color) with the suction cup attached to the CRT is the high voltage lead. If you disconnect it from the CRT, you can get zapped if you get near the connector under the suction cup.

Capacitors in the power supply can also hold a residual charge, but they usually are discharged through the circuitry they are attached to. Some caps in the newer sets with switching power supplies can hold a charge.

Not to say you can't get a good shock, but I've been zapped by both CRT's and caps, and you usually do more damage by the sudden jerk of your arm then the actual "shock" you get.

About half the televisions I fix are bad solder connections. (Hence the earlier suggestion of banging on the set.) Generally if it isn't a bad solder connection, they usually aren't worth repairing, because new ones are so cheap.

[This message has been edited by FrugalFiero (edited 12-05-2007).]

I am glad some of you mentioned how to discharge the system, I nearly forgot about that, reminder is appreciated.
The info about capacitors and weak or inferior solder connections is what I need, the possiblilites of what could cause this and what to look for first. Also was not sure if there was a replacable part or unit that would control the brightness for an easy fix.
By the way the TV is a Sharp unit, 40 something inch screen but I don't have the specifics in front of me at this time. I will look in to this over the weekend, need to work OT for the holidays.

40"??? sure its not a rear projection? and the fan for the bulb is just cooked, and it shuts the lamp due to heat?

quote Originally posted by FrugalFiero: OK, lets try to get this straight. I have worked on televisions for 30+ years. Believe me, CRT picture tubes can hold a charge. There is no "cable" in any CRT set (new or old) that I know of that discharges CRT's. You can manually discharge a CRT but you should know what you are doing before attempting it. The cable (usually red in color) with the suction cup attached to the CRT is the high voltage lead. If you disconnect it from the CRT, you can get zapped if you get near the connector under the suction cup. Capacitors in the power supply can also hold a residual charge, but they usually are discharged through the circuitry they are attached to. Some caps in the newer sets with switching power supplies can hold a charge. Not to say you can't get a good shock, but I've been zapped by both CRT's and caps, and you usually do more damage by the sudden jerk of your arm then the actual "shock" you get. About half the televisions I fix are bad solder connections. (Hence the earlier suggestion of banging on the set.) Generally if it isn't a bad solder connection, they usually aren't worth repairing, because new ones are so cheap.

He means the cable around the outside of the tube. If you follow its connection it goes to ground.
And you are right about capacitors. You would have to try really hard to kill yourself with one of them.

Now, is this a projection TV or a CRT?

Knowing someone that does this for a living for about as long, if not longer, than Frugal, the problem is likely not going to be apparent by someone who has never had to fix a TV before. If its a dirty solder joint, thats easy, but if its a bad component it wont be simple.

[This message has been edited by AP2k (edited 12-05-2007).]

quote Originally posted by AP2k: He means the cable around the outside of the tube. If you follow its connection it goes to ground. And you are right about capacitors. You would have to try really hard to kill yourself with one of them.

no, he's right....I thought that large cable at with the sucker cup connection was a ground.....

quote Originally posted by Pyrthian: no, he's right....I thought that large cable at with the sucker cup connection was a ground.....

THAT cable, yea. Its the HVDC connection. But there is a cable around the outside edge that is there to discharge the tube.

quote Originally posted by AP2k: But there is a cable around the outside edge that is there to discharge the tube.

If you are talking about something that looks like this:



These are the different types of CRT degaussing coils. They are placed around the CRT to remove residual magnetism. They have NOTHING to do with the residual electrical charge stored in the CRT.

The CRT also has a braided ground cable or spring loaded to contact the conductive "DAG" coating on the glass envelope of the CRT. This would be "ground", however this ground doesn't magically discharge the CRT either.

The only way to discharge a CRT is to manually do it youself. see below:



You can use a screwdriver for a discharge tool, but you better be holding onto the insulated handle.

So in the picture below:



The red wire with the suction cup mounted on the reddish part of the back of the CRT is the HV anode connection.

The black cable draped around the dark part of the CRT is the degaussing coil / winding.

The silver braided cable running near the degaussing cable and down towards the chassis of the television is the ground cable.

Whew!

[This message has been edited by FrugalFiero (edited 12-05-2007).]

The TV has been this way for over a year, not exactly sure of the correct size but I will measure that up tonight if I gat a chance as well as get the model number.
Thanks for all the help and the info guys, I appreciate it. With any luck I will have the TV going again and be able to use it. This is more for my dad than anything since I have a large screen TV at my house, he has been useing a 12 as of late and has no desire to buy a new TV as I do not feel like spending the money as well on a new TV. Just another expence that is not a nessesity, but if I can get this TV to work than all will be better with little to no money being spent, that I can live with.