No picture. Low EHT ?

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LG ctv model CT-25Q26ET


Fault - Black screen, no picture or on-screen display. Sound O.K.

If I short the red, green and blue pins on the crt to ground, I get a
full screen of that colour.
During that time I can barely see a faint tv program picure.

Adjusting the screen control makes no difference to the brightness, but
the focus control does
make some differnce.

Is low EHT from the transformer the likely cause?
I do not have a high voltage probe.
After I turn off the ctv, I can get very little spark when I discharge
the picture tube.

Other voltages from the transformer and the B+ appear to be O.K.

Can anyone suggest anything else I should check before ordering a new

Russell Griffiths.

Re: No picture. Low EHT ?

On 16 Jan 2007 22:07:09 -0800, ""

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A symptom of low EHT would be a large raster. You would probably also
see lower than normal G2 and focus voltages. I'd also check the other
secondary voltages, eg the supply to the video amps, heater voltage,
etc, but you say that you have already checked these.

You could try to make sense of the HR Diemen equivalents:

Each variation has a schematic diagram with voltages.

- Franc Zabkar
Please remove one 'i' from my address when replying by email.

Re: No picture. Low EHT ?

I would suspect problem around the RGB amplifier. How is voltage to to teh
RGB amps? Usually 180-200V.
I do not remember his model, but if it uses RGB amplifier on a chip, I would
replace this chip first.


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