TV repairable?

Page 7 of 7  

PE wrote:

If the problem gets better suddenly, then look for bad solder joints (can be invisible without strong light and a magnifying glass), but if it gradually improves, suspect a worn-out capacitor. As people much more knowledgeable have said, the fault is in the horizontal deflection circuitry. The PC board should be labelled by section, or you can trace the 4-6 wire cable going to the yoke of the CRT (yoke is that big coil around the neck).
Be careful not to let the TV fall forward, which it can easily do because its center of gravity is only 2" behind the screen. One person mentioned placing a CRT on a bed and seeing it fall forward and tumble to the floor, so either place it on a solid horizontal surface, or place it face-down on a soft surface.
Apparently Japanese CRT TVs at least 15 years old were built better than newer ones and had CRTs that would last a long, long time. I'm still using a 34-year-old Sanyo that still works well and has needed only 2 new capacitors.
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I forgot to mention that your local library may have Sams Photofacts manuals online for free, and ElektroTanya.com has many factory repair manuals
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I had a CRT that would go red after being on a few minutes. I took the cover off and while it was on, poked around the components with a 2 foot wooden dowel until I found one that resolved the problem when I held pressure on it. Unplugged the TV and checked that board from the other side (staying well away from any big caps) and found a circular crack in the solder around one leg of that component. I remelted the solder and it was fine for several more years.
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On 1/16/2011 9:18 PM, PE wrote:

I just wanted to some what you can realistically do.
This is likely a cap problem. If you look at the top of an electrolytic cap it will have a cross scored "vent" on the top of the cap. Damaged caps will often appear slightly bulged there. Look for one and replace it with one of the same value and the same or higher voltage rating. The negative end is marked, make sure the polarity is correct.
This may, or may not, fix your problem. But it is in the low dollars to try.
Jeff
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yeah,if you don't,they burst and spray nasty,icky,smelly stuff (and foil,too)all over...from personal experience! ;-)

you may also see a discolored cap body,compared to others on the board.
--
Jim Yanik
jyanik
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On Sun, 16 Jan 2011 18:18:08 -0800, PE wrote:

The effect's called pincushion; it's unlikely to be the CRT itself - chances are a bad capacitor in the horizonal deflection or something specific to the pincushion correction circuitry (bad transistor, bad solder joint etc.)
See if you can find a schematic online. Might take a bit of digging because some chassis are shared between manufacturers or between models from a specific manufacturer, and the schematics are often filed by chassis designation rather than whatever manufacturer / model number is printed on the back of the set.
Gotchas:
1) TVs are about the worst-built of any consumer appliance; just about everything's designed to be as low-cost as possible so that the TV works when you buy it but doesn't necessarily last for long. Bad solder joints aplenty, and cracked PCBs aren't unheard of. You may be looking for a mechanical fault rather than component failure.
2) Some capacitors fail in an obvious way - sometimes with can-style electrolytics they'll visibly bulge and split and show signs of electrolyte leakage. But most don't die that way, and you'll need an ESR meter to detect faults (the other approach is to trace the fault to the most likely area and simply replace all caps in that area)
3) Serious voltages inside a TV, and stored after the set's switched off. I've only been zapped by a TV's HV once, but it's not something I'd care to repeat - unlike the brief ouch from an outlet shock, TV HV *hurts*. Be careful (if you've been inside TVs before you probably know this, but I figure it doesn't hurt to mention it :-)
There's a huge amount of useful info on the repair of TVs at:
http://www.repairfaq.org/samnew/tvfaq.htm
Anyway, yes, it's fixable - but only you can decide whether you want to invest the time :)
cheers
Jules
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