faint green picture


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faint green picture

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robertdench
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Dec 20, 2005, 5:59 PM

Post #1 of 6 (1154 views)
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faint green picture	Can't Post

Hi

I have a 32" widescreen toshiba about 3 years old.

Fault is that there is a green fog over the whole of the picture.

I started out thinking it was a heater cathode fault as disconnecting and switching the video drive outputs on the CRT neck board had no effect, so tried the heater isolation trick. No joy. Still green. (At least I know how to do this now)

Have disconnected ALL of the video drive signals to the CRT neck. This should mean black screen, but as the tube warms up, a faint green picture appears at the centre of the screen.

What is going on? How can this be? All I can think is that one of the other beam control grids must be being modulated somehow! Help.

Rob

canhelp
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Dec 21, 2005, 3:16 AM

Post #2 of 6 (1148 views)
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Re: [robertdench] faint green picture [In reply to]	Can't Post

green gun short, boost it.

robertdench
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Dec 21, 2005, 10:32 AM

Post #3 of 6 (1143 views)
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Re: [canhelp] faint green picture [In reply to]	Can't Post

Hi canhelp, green gun short to where? what do you mean by boost it? where is the picture coming from? could it be a cap around the flyback?

cheers rob

denonjapan
Veteran

Dec 21, 2005, 10:50 AM

Post #4 of 6 (1141 views)
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Re: [robertdench] faint green picture [In reply to]	Can't Post

OK, have you not touch or adjust any inside of the tv? if so, DEGAUSSE the whole screen gradually till the green fog disappears.

your tv must be exposed from ultra magnetic forces from your speakers magnet. therefore you need a DEGAUSSER.

denonjapan

made in japan

canhelp
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Dec 23, 2005, 1:26 AM

Post #5 of 6 (1130 views)
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Re: [robertdench] faint green picture [In reply to]	Can't Post

what's your TV's model? ok, generally, in toshiba's schmatic it's just simply called G (anode, in Sony, called KG). It's G short or nearly short to Ground(you may call it G1-if I remember it correctly - which is connected with ground in many video drive circuits). Boost means you use high voltage to remove the short.

If anode is deposited by oxidized barium. It is going to get closer to G1. In this circumstance, even if you disconnect all 3 colors' drive. There is still some electrons emit out-- image the electric field between G to G1.

In your case, it is definitely not cuased by cap around the flyback -- I can not find any reason.

I HAVE NO FUN IN NORTH AMARICA, SO I GO TO INTERNET TO PRACTISE MY ENGLISH.

rrobor
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Dec 24, 2005, 10:20 AM

Post #6 of 6 (1119 views)
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Re: [robertdench] faint green picture [In reply to]	Can't Post

Yes its the tube, Im surprised its not cathode heater as that is the usual, are you certain you drove the heaters with a totally isolated from chassis earth feed? Other than that put the set on its face switch on and tap the tube neck, Ive cleared a few like that. Another trick is to get a 10uF electro charge it up to a few hundred volts then discharge it across the shorting pins of the tube

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