Re: UPDATE: TV Missing color diagnosis

After checking the CRT neck board again and found no obvious faults. I checked the driver signals and found that the Blue drive is double of that of the other two guns.
As previously stated I am sure i noticed that the cathode voltage had equalised after a few minutes of running, but coloured hue was still present.

Will trace back further and see what else I can find. So maybe it isn't a CRT output drive board then...


TEX



TEX wrote:
Confirmed it is not a color driver feed issue. Found a schematic for another model TV and from that worked out which wires were the control/drive lines. 5 wire connection RBG gnd and 12v. All the input drives give value of around 3.1v. Swapped drives and confirmed they working.

So confirmed it is either a CRT fault or neck board fault. I was hoping that since the voltages i was getting at the driver transistors are the same weather the board is connected to the CRT or not, then it is board board.

Where to next??

TEX

James Thompson wrote:
"TEX" <tex@xxxxxxxxxx> wrote in message news:1154258261.420666@xxxxxxxxxx
Been working on this 29" TV and cannot work out why the voltage on the one of the driver transistors is low. Drive transistors located on the CRT neck board.

Blue =120VDC
Green =195VDC
Red =195VDC

Green does show up on the screen but very dull. Red/magenta hue. Am i correct to say that the blue it under driven causing the complementary color to produce the hue. Or are the other two guns over driven????

Since there is green am i to assume there is nothing wrong with the RGB IC and it is still just a driver circuit problem

Where to diagnose from next??? Just stuck on this cos never come across it before.

Thanks

TEX

You can see if it may be a driver problem by switching color drive feed wires to the crt board. As in switch the red with the green and see how bright the color is driven. This may eliminate the problem from the color output from the chassis and you can concentrate your effort to the neck board. If the green is bright after switching with red driver, then you will know the green driver is weak (not the output on the neck board). Jtt


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Relevant Pages

  • Re: UPDATE: TV Missing color diagnosis
    ... Found a schematic for another model TV and from that worked out which wires were the control/drive lines. ... So confirmed it is either a CRT fault or neck board fault. ... I was hoping that since the voltages i was getting at the driver transistors are the same weather the board is connected to the CRT or not, ...
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    ... of the driver transistors is low. ... Drive transistors located on the CRT ... You can see if it may be a driver problem by switching color drive feed ... will know the green driver is weak (not the output on the neck board). ...
    (sci.electronics.repair)
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