Philips 42PF7320 plasma, strange problems

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Re: Philips 42PF7320 plasma, strange problems

The powerboard models for this TV have a cluster of dodgy 680uf 50v Samwha WB capacitors under a heatsink. Any cap that goes under it must be less than 30mm high. The only cap I can see that might be suitable and fits is the Rubycon 50ZLJ680M12.5X25.




Is the Rubycon ZLJ's being rated 0.025 for impedance versus 0.020 on the Samwha WB going to be a problem? In other words, is the Rubycon ZLJ an appropriate replacement?

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Re: Philips 42PF7320 plasma, strange problems

Ok, so the 8A fuse giving 0.1 to 0.3 probably means it is still working normally? Does the lack of relay clicks specifically mean a fuse or fuseable resistor is blow?

If this power supply board is effectively unrepairable, can I swap in any working LJ44-00101B / LJ44-00101C replacement powerboard, or is television model-specific setup required to supply correct and operationally safe voltages?

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Re: Philips 42PF7320 plasma, strange problems

Test these two resistors while the TV is off. I think they should measure 6.8 ohms each.

The one on the left gives 6.8, the one on the right varies from 6.8 to 7.0. They both have 6.8 written on them.

Test this fuse also while off. I think it should measure less than 1 ohm.

It gives 0.1 to 0.3 if I touch the two points on the back of the PCB, and 1 to 3 if I touch the fuse directly on the front of the PCB.

Also test the resistance of your meter leads - touch both probes together and note down the measured resistance.

It jumps around alot and comes to zero.

[tom66]

Re: Philips 42PF7320 plasma, strange problems

Unfortunately, I do not have a meter, so I would have to get one, but I'm not sure about how to tell the good from the bad in that area over what is needed to test a power board.

A multimeter is fairly cheap. Whereabouts are you?

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Re: Philips 42PF7320 plasma, strange problems

Unfortunately, I do not have a meter, so I would have to get one, but I'm not sure about how to tell the good from the bad in that area over what is needed to test a power board.

[tom66]

Re: Philips 42PF7320 plasma, strange problems

Test these two resistors while the TV is off. I think they should measure 6.8 ohms each.

Test this fuse also while off. I think it should measure less than 1 ohm.

Also test the resistance of your meter leads - touch both probes together and note down the measured resistance.

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Re: Philips 42PF7320 plasma, strange problems

pic attached

[tom66]

Re: Philips 42PF7320 plasma, strange problems

That would mean up to 15 capacitors in all may need replacing.

What I would like to know is whether it's worthwhile attempting to replace these caps, that is, what concerns me is what the lack of relay clicks means and whether replacing the capacitors is likely to fix it?

It's possible you now have a more serious problem. Can you post a picture of the power supply board? Then some tests can be highlighted.

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Re: Philips 42PF7320 plasma, strange problems

That would mean up to 15 capacitors in all may need replacing.

What I would like to know is whether it's worthwhile attempting to replace these caps, that is, what concerns me is what the lack of relay clicks means and whether replacing the capacitors is likely to fix it?

[tom66]

Re: Philips 42PF7320 plasma, strange problems

Subtly rounded sounds a lot like bulged to me. If they are not completely flat, they have failed, or are about to. It certainly sounds a lot like a power supply unable to cope with transient or sudden changes in loads, bad caps can cause that.

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This TV had two problems. It would intermittently drop into standby mode while operating. And when the entire display area changed between scenes at once, the panel would sometimes blank out for a moment.

After dropping into standby, the TV would need to be unplugged and replugged before it would turn on again.

I opened the service menu and an error 11 was registered. The service manual says this is an "I2C error while communicating with the 2D/3D combfilter Columbus". Could that have just been from low voltage?

Then the TV wouldn't turn on at all - the relays clicked twice, the red LED showed momentarily then it clicked off.

The front LED never displayed any blink codes except for the second to last time the TV turned on the front green LED blinked infinitely.

There are no burst capacitors on the power board (a Samsung LJ44-00101B PS-424-PH Rev0.65) nor does anything there look cooked. But about 2/5ths of the caps have subtly rounded quadrants whereas the rest are totally flat on top. Is this some manufacturing variation or the result of pressure buildup? These are Samxon KMOD caps from 2005.

I tried unplugging everything from the power board except the mains power connector. It still clicked thrice. After that, it won't click at all now. Is this normal behaviour when the PSU is in isolation? Does this indicate blown fuses? Would it be dangerous to the TV to plug everything back in and try again?

I found a repair tips guide for the power board (search "Philips PS- 424-PH LJ44-00101C PSU.pdf" ) that describes how to provoke the power board to display an error code, but I don't have he necessary shorting jigs and am a bit wary of trying to connect the pins directly as they are so close together.

Could this all still be consistent with just Samwha C8059/60 failures? The power board does seem to be the root of the problem but this is unlike the difficulties it has given others.
So I'd be thankful of any tips.