Help in Fixing TV

K

krys_k

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#1
I realise that this is a satelites forum, but I'm not sure where to turn or find out the information I need.

My colour television sporadicaly (and periodically) turns black and white and then for no apparent reason, it turns back to colour.

Is there a way to fix this problem?
Is there a community such as this one that deals with television issues, where i could find out this information?

any help would be great.

many thanks

krys_k
 
Llew

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#2
krys_k said:
I realise that this is a satelites forum, but I'm not sure where to turn or find out the information I need.

My colour television sporadicaly (and periodically) turns black and white and then for no apparent reason, it turns back to colour.

Is there a way to fix this problem?
Is there a community such as this one that deals with television issues, where i could find out this information?

any help would be great.

many thanks

krys_k
Might help if you say which receiver you have, though can't guarantee it.

I've shifted this to a more appropriate section.
 
gameboy

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#3
Bet it's a Sony!
 
B

bulmers

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#4
If its a Sony , The trimmer beside the pal decoder ic might need adjusting.
 
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krys_k

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#5
Yes its a Sony!

To be honest with you - I don't know what a trimmer beside the pal decoder ic - could you let me know if there is a diagram anywhere on the net for it?

Also how does one adjust it?

Many thanks

krys_k
 
Llew

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#6
Working in the dark here without knowing the model number, but you need to locate the PAL decoder section (might be a seperate circuit board) and find the crystal - a thumb-nail sized metal box with either 4.433619 or 8.867238 written on it. Adjacent to this will be the trimmer - usually a round gold-coloured component. This can be carefully adjusted either way until the colour returns.

DON'T poke around inside the set if you aren't confident. There's some killer voltages in there. Best to switch off, adjust, then switch on again.

Llew
 
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steffan_st

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#7
I'd say you have bad solderings somewhere in your telly,almost always the case when you have intermittent problems like the one you describe.
 
K

krys_k

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#8
Thanks ever so much for your helpfull replies.

I took the back of my tv off, but couldnt find the components you mentioned. The tv is a Sony Triniton Model No. KV-M2151U - would you know where PAL decoder and trimmer are?

also my other tv, again a Sony Triniton, this time model no KV-X2952U has developed a fault - the sound fluctuates and crakles. also it has a purple hue in the top left corner. any help here would be great.

I appretiate all your help. Many thanks.
 
Llew

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#9
Your other TV's colour problem is almost certainly a faulty deguassing posistor.
Can usually be replaced easily.

Might be able to find out something for your other faults.

Llew
 
BGonaSTICK

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#10
krys_k said:
also it has a purple hue in the top left corner. any help here would be great.
:( Mine did that when I left it next to my enormous speakers. It never did recover...
 
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buzz

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#11
From experience.......A majority of the problems found with Sony TV's are from Bad soldering connections that breakdown over a period of time either due to heat or high frequency making the connection actually oscillate break the solder connection. I recommend that the 1st thing to try would be to gently tap the circuit board with a NON-CONDUCTIVE item like a plastic pen to see if you could make the problem intermittant. If you can them continue to gently tap to see if you can localize where on the board it becomes more evident. This will help you find the poor solder connection. Like I said, it is very common for Sony's to have this problem. Good luck
 
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#12
buzz said:
From experience.......A majority of the problems found with Sony TV's are from Bad soldering connections that breakdown over a period of time either due to heat or high frequency making the connection actually oscillate break the solder connection. I recommend that the 1st thing to try would be to gently tap the circuit board with a NON-CONDUCTIVE item like a plastic pen to see if you could make the problem intermittant. If you can them continue to gently tap to see if you can localize where on the board it becomes more evident. This will help you find the poor solder connection. Like I said, it is very common for Sony's to have this problem. Good luck
I use a toothbrush, the bristles will allow each soldered joint to be moved a micron or so, allowing a pinpointing of the bad ones.

(always turn off and unplug before soldering. I forgot once after becoming distracted, it shows)
 
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buzz

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#13
and make sure it's dried off...heh..heh..heh...
 
K

krys_k

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#14
Thanks for your help.

I took out the board and couldn't find any dodgy soldering - it all seemed as it should be. However, by using a toothbrush I indentified one of two components that when tapped colour returned. I am not sure which of these two is the guilty party.

The first component was a flat, retangular box, with metal 'legs' running down both sides (aprox 5mm x 20mm). It was labelled

TDA4510
22 1220
DSD95098

The second (and i think more likely) was a black cylinder, aprox 30mm hight and with a radious of 8mm. It was labelled on one side:

(M) 85*C
4(2)
Nb

And on the other:

16 SME
2200 V
mF

Does this make sense? Is it one of these components, or am i missing a soldiering point? What should my next step be?

Many thanks for your help. I really appretiate it.
 
Llew

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#15
Well the TDA4510 is the PAL decoder chip, the colour processing IC, so that or an adjacent component may have a dry joint.

The other component is an electrolytic capacitor, depends where it is in the circuit as to whether it's the culprit.

If you're handy with a soldering iron, go round the IC and other components nearby and resolder the legs.

Llew
 
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spiney

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#16
When picture goes monochrome, set has "lost" chrominance signal, often only because the tuning has drifted, did you try retuning? (do it with AFC off, if possible).

Intermittent problems are usually heat related, bad contacts or dry joints "crack" as they warm up. When switched on, does your set start off ok, then problem appears after 20 mins or later?

For PAL crystal trimmer, wiper might "disconnect" from track, try very gently pushing down on the circular metal bit, be careful not to break it, might just do the trick, it shoudn't make it worse.

In general, it's not a good idea to "twiddle" things randomly, without access to test equipment and service manuals (but repair technicians see this frequently!).

Tube colour purity problems are from stray magnetic fields (that's why "home cinema" loudspeakers are shielded!). There's an internal degaussing coil, in series with thermistor, this operates when set switched on, then "drops out" after a few seconds. For bad magnetisation, this isn't enough, then you need a service technicain's degaussing coil, rub it over screen front, slowly pulling away. Trinitrons are very susceptible to magnetisation, because of their internal structure.
 
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Satenq

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#17
I think you should be discouraging krys_k vbmenu_register("postmenu_200134", true); not encouraging him to delve into the rears of a tv set, criky he doesn't even know what an electrolytic looks like, which would also suggest that he has no soldering skills, what if he goes in and the main cap is still charged?
 
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#18
Satenq said:
what if he goes in and the main cap is still charged?
He gets a lesson he wont forget about high voltage discharges from inside to outside the telly via his fingertips?? :p

O-Ha
 
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