PHILIPS 42PFL7404

[biogon]

My 12 years old TV set is a PHILIPS 42PFL7404, the PS is a DELTA DPS-298, and the LG panel is LC420WUF. Three weeks ago the screen starts blinking slightly and a minute later went black, but with audio. I desconected from the power line, power on again and in a few minutes the same problem. I removed the back cover and all the PS components look good. Power up again and the problem disappears, go into the service mode and find (Error code:17) and 11000 display hours. Put the cover again and the screen goes black in 2 minutes. Then check all capacitors, diodes and Mosfets, resoulder the main connections, update the firmware and close the back cover. Two minutes after power on, the same problem. Remove again the cover and using a heather fan at 100ºC I found a sensitive zone that generates the same problem in a few seconds. But the back side smd componentes involved are from the feedback (zener and opto) and supervision of the main switching PS secondary and not from the inverter circuits. I suspect the CCFL tubes but I have doubts with the PS...

[dick_barton]

Re: PHILIPS 42PFL7404

If you warm up the opto and zener and the fault returns quickly then you cool the opto and zener, does the fault go away just as quickly. If so I would consider replacing those components first.

What zener and opto? On the power supply or mainboard?

[biogon]

Re: PHILIPS 42PFL7404

If you warm up the opto and zener and the fault returns quickly then you cool the opto and zener, does the fault go away just as quickly. If so I would consider replacing those components first.

What zener and opto? On the power supply or mainboard?

These componentes are in the PS: IC953(TL431) and the opto PC901(NEC2561), but some other componentes round.