HI Abraham,

thanks for that updates and I checked  through the link and it was very informative, thanks a lot, now could I ask you ( in my schematic)

is  the flyback pulse from the FBT  is  necessary to turn ON the power supply, if you observe fly back pulses are feed to pin No, 10 of the

power Ic, what if the flyback pulse is cut off  can this cause a immediate shut down. Can the TV be powered by a 115v power supply that does

not require a flyback pulse for start up?…..The schematic as such is bit complicated and hence  please enlighten me on this.


Sorry i do not have the full schematic. I just got the power supply schematic and it does not have the flyback. Anyway, there is a possibility that the full power will be only generated if there is a feedback from the flyback. But the feedback have to be energized first, that means it must first receive the B+ voltage and the pulse to the HOT in order for the flyback to generate pulse back to the pin 10 of power ic.

Jestine

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1. I am repairing a AOC 15″ VGA monitor and found a wire wound resistor
and a FET(Mosfet) both short circuit in the primary side of the power
supply section. I managed to get the replacement for FET but unable to get the wire
wound resistor. The value of the wire wound resistor is 33K 2Watt,
can I replace it with a carbon film resistor with value 33K 2watt
or 33K 3watt?

What is the difference between wire wound and carbon film?

HI Austin,

Wire wound could withstand higher surge current as compare to carbon film. I suggest that you use the 3 watt carbon film better.

Jestine

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HI Gopal,
How r u. Hope u fine.

I’m fine thank you.

I have two simple questions please clarify it.

1. How to identify that EHT is working at full efficienty if there is no light and B+ supply voltage is normal. Screen voltage is 120v max after disconnecting from CRT board.

Use high voltage probe. If you got 18kv instead of 24 kv you will know that the flyback is not working at full efficiency.

2. How to insulate a EHT if there is sparking at body of the EHT or it should be replaced. (but it is in working condition)

Replacement is the best solution.

3. In one monitor HOT was short. When i changed the HOT and started, a heavy sound appeared from EHT cap (i think, not sure) and HOT shorted again. No other component found faulty in EHT section. I hope EHT internal capacitor may be weak so i planned to change the EHT but it is not available in the market. How to confirm about the EHT fault. Should i use series lamp test with HOT. Ring tester shows EHT Ok.

It could be the B+ voltage too high or the safety capacitor have problem.

Jestine

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HI Achour,

hello mr jestine; i am face a difficult problem with 17″ crt monitor; the vertical ic of this monitor

( tda 8172 ) blows with a filter capacity ( 220 uf  25v); i have replaced it with a good one and voltage, surrounding component are correct. when power on the monitor the circuit become very hot and blows after some hours to some day of working.

If the same vertical ic blows again then you may need to check if the supply voltage really correct and stable. Make sure you apply the heat compound so that the ic can transfer heat faster. If it still blow then perhaps the vertical yoke coil winding may develop a short circuit after the monitor is heat up.

there is a strange phenomena that happens; when i switch the resolution of the monitor to 1024 x 768, a horizontal lines appear on the screen and we can heard a sound ( i think near the smps supply area ).

THANKS

Try replace the horizontal/vertical ic and retest.

Jestine

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