I wish to repair my own T.V

[flyer 10]

I'm just fooling around but i wish to repair my own 4yr old 27in Sony,it glicked off acouple of times then packed up for good as in no pic,no sound,in fact a complete black screen, ihave enough electic knowledge not to touch anything with power,any pointers would be helpfull (when pluged in thepower clicks on &off but no light) thanks for any help.

[ASPGuru 10]

Without test gear, a schematic and some bits to swap in and out there's not a lot you can do.

 

Having said that...

 

TVs, like computers, can suffer from thermal creep. The cycle of powering up and off causes stuff to expand and contract due to the heat, and over time this can cause things like connectors (rarely) and chips (occasionally) to move enough to make a bad connection in their respective sockets.

 

Leave the mains cable attached to the wall socket BUT WITH THE POWER OFF. This allows the TV to be earthed, but safe. Then just make your way round the various cables and chips and try reseating them. If possible, use just one hand, and keep discharging any static electricity by touching any metal case parts you may see.

An anti-static wrist strap would be useful, on the hand you are using. Try to avoid creating an electrical path across your heart - do anything you can to avoid random electricity! In older TVs there are some huge capacitors (not so sure about modern ones) and the voltages around the back of the tube are much higher than you think.

 

Use a small brush and the vacuum cleaner to get rid of all the dust that will be in there.

 

I managed to repair one TV by taking the actual mains switch apart and cleaning the contacts. Can be extremely fiddly.

 

You may get lucky, but I've two TVs in the attic that died in the same way, but I refuse to throw away as I'm convinced there must be a simple reason. After a number of years I've been unable to find one, and not being a TV engineer I have no idea what half the bits do!

 

Every six months or so I power them up - just to see if a rest has cured them! Got one TV back that way, but the other 2 remain 'resting'.

[Grahame 10]

You will be lucky, but the fact it powered down and came back up again might indicate a dry joint. You can try soldering round the power supply and the Line Output Transformer as that is where the LT is derived from. Other than that, you are best off leaving it alone.

 

(This is basically what ASPGuru was saying)

[littlebasher 11]

You may wish to read this first before you go poking around inside.......

 

High voltage: CRTs operate at very high voltages, which can persist long after the device containing the CRT has been switched off and/or unplugged, sometimes for years. Residual charges of hundreds of volts can also remain in large capacitors in the power supply circuits of the device containing the CRT; these charges may persist. Modern circuits contain bleeder resistors, to ensure that the high-voltage supply is discharged to safe levels within a couple of minutes at most. These discharge devices can fail even on a modern unit and leave these high voltage charges present.

 

Make sure your voltmeter is rated at 32,000 + volts to measure this high voltage presence. It is likely that a special voltmeter will be needed as most common ones don't read voltages that are in that range.

 

Those working inside CRT-containing equipment should know how and be able to safely discharge these hazards . (See Samuel M. Goldwasser repairfaq.org link) In particular, the large rubber connector which looks like a suction cup is responsible for supplying accelerating voltage to the bell of the CRT. Under the suction cup is the ultor, which couples the accelerating voltage to the inside of the tube. Inside the glass bell is a coating of metallic paint, while the outside of the bell is coated with a conductive graphite coating called Aquadag; between the ultor's connection to the flyback transformer and the Aquadag, there is therefore a capacitance capable of maintaining the full accelerating voltage for weeks. While this accelerating voltage is high (typically from 7 kV to 50 kV depending on screen size, monochrome or color, direct view or projection), both the capacitance and flyback current are small (on the order of picofarads and nanoamperes respectively), so shocks from the accelerating voltage are typically embarrassing and painful but usually harmless. On the other hand, the voltages and available currents used in the deflection and power supply circuits can result in instantaneous death.

[upinwath 10]

It's quite clear that your troddle has come clean away from your trodleratchet. Unless you have a troddle spanner and a TR testing meter you have no chance at all of resetting your plonkledonkey.

 

That or the clicking may well be the lopt that's buggered.

 

You know the old ad that proudly said "It's a sony" well the engineers used to say the same but in a more sarcastic and downbeat way.

Look great while they work but a bag of crud when they fail.

 

PS if anything in the above made any sense you were making a lucky guess or you need to toss the thing away before you kill yourself or someone else.

[melthebell 863]

unless your experienced in repairing tvs DONT touch em

as has been said crt tvs keep a charge looooooooooooooooooong after its switched off

 

we dont want any fizzle fizzle KABOOMS round here

[flyer 10]

Thanks and i except all your advice ,ihad never heard of Samuel M. Goldwasser befor,&tracking down via internet i found him a wealth of info,Sony does seem to have a built in problem,abiet easly fixed by repair man ,at least now if i'm told it needs 4new tires &apaint job i can ? his findings.