Sony Trinitron TV KV 28ls35u - colour problem

[antronic]

Hi Folks

I rescued this Sony TV from the street, which I'm trying to fix up.
The power lead had been torn of, so i opened it up and attached a new one to the board.
When i turned it on it looked like this with my dvd plugged in

you can see the picture is sharp, and the colours are ok top left, but disort all the way out from there as the screen should have looked like this

I've read around and it seems this could be a deguass problem which i could fix, or a 'screen mask' problem, which I could not.

Could anyone diagnose which from looking at the pictures of the screen?

Thanks very much for you time and help in advance

[NST]

It's difficult to tell, but it's more likely to have been thrown out due to a degauss problem. You should hear a sound when the TV is first powered up, followed by a relay clicking off a few seconds later. If this is not the case then it's likely that the degauss posistor needs replacing.

I think you might be able to degauss the Sony if you unplug both TV's from the wall, then place the working TV screen-to-screen with the Sony, then power on the working TV closely followed by the Sony. With a bit of luck the working set will degauss the Sony, and you'll have your answer.

[antronic]

Thanks NST, I'll check and try that when i get in,
fingers crossed...

[antronic]

when i turn the set on i get a soft hiss, then a click straight after, (less that a second after pressing the button)

So i've tried the screen to screen thing as described several times, but have seen very little change

if you look close you can see the patch has shifted slightly.
[however the tv is now facing in a different direction to before so could the earths magnetic field have affected it?]

Do you think its worth me continuing with this process?
I have a soldering iron to hand, and read you could degauss with that too; would it be better?

Another thing - when i had the back off the tv, I noticed a lead that was hanging lose.
I think it was 2 wires, blue and white, small white connector on the end plus I saw a likely looking pair of pins, on a board under the tube, where it might have wanted to connect to.

I should probably try plugging thart in, you think?
I'm aware there is some high voltage in there, so would have to be very careful

any ideas apreciated
ta

[NST]

Yes if there's a cable loose, by all means plug it back in! I'm guessing that this is probably for the degauss coil that you can see running around the back of the tube (thick black wire).
Disconnect the set from the mains (plug out of the wall) before doing so. If the set has been on already, give it about an hour before powering up again.

[antronic]

Yep, that was the degauss coil connector that was unplugged, doh.
After i plugged it back in and turned on the set, it made the propper noise and showed a much improved picture

however its not improving any more at all after repeating the process several times.
I leave it off for upto an hour, then turn on and hear the "dwonk" sound but the picture remains exactly the same. (i know its exactly the same because i keep taking photos...)

Do I just need more patience, and should keep turning it off and on, or should i start looking at something else?

Thanks again for all advice

[mechanic]

It sounds and looks very much like the shadow mask in the tube has shifted and there is nothing you can do to fix this.Why the degaussing coils were disconnected is a bit of a mystery though.

[NST]

I agree, this is not fixable so best to have it sent to a recycling facility or list it on eBay as faulty (suitable for spare parts etc).

[antronic]

Thanks for your advice folks, it was quite interesting taking it apart anyway.

I decided to take the speakers out before I get rid, with the intention of sticking them in my car for some lo-fi sound
But its hard to believe how good they sound considering I have just shoved the in a couple of shoe boxes!!!

I packed a bit of foam behind them to hold them in place, and cut a whole in the front of the tweater, and all together they make quite a respectable noise

cheers for all the advice

[Kitjunky]

Replace the degaussing thermister, common fault on all crt sets and should cost no more than a tenner. it will be close to the degausing coil connector and connected directly to it. its a 3 pin device, could be square or round

[antronic]

Hi Kitjunky

how likely do you think that it is this thermistor thats at fault, considering the images and comments above?
ie it did degauss and improve once the first time i connected it - now pattern has has remained constant, after many cycles on off - also i hear the degauss coil 'dwonk' when i turn it on

I was just about to dispose of it as the other folks above considered it unfixable?

[Archie Fax]

Can't you get it looked at by a tv engineer? This would save you guessing.

[antronic]

Hi Archie
I was just having a bit of fun with a found telly really. Not worth spending money on an engineer on it on the off chance - so its off to the dump with it now (I got some interesting speakers out of it at least
cheers all

[antronic]

As a footnote, yesterday i picked up another 28" widescreen from the street - this one only needed a power lead and a fuse.

Its a nothing special Beko but, the pictures fine (thats just some reflection on the screen) and for 30p for a fuse , who could complain.

Cheers all for the inspiration