Philips 42pfl5432d backlight

[Dgtech]

Re: Philips 42pfl5432d backlight

I never believe people who say that.

I hate it when you're right.

Well, as I said before, the unit wouldn't power up at all.

Upon taking out all the screws, I notice one missing, CRAP. Now I'm looking for more signs that its been worked on already. Yeah... recap done already to 3 caps out of 4 usual capxon's. Why they stopped at only 3, who knows. Maybe those were the only ones bulging. Then I look down and see a burn mark under the two diodes... CRAP. Its lifting a trace on the other side of the board and possibly damaged R930 - surface mount. Checked the main fuse, CRAP, It's blown. Deep breath....OK, time to go to work on this thing.

I got to pull those two diodes and see what part number they are and verify polarity. The strange thing is that they aren't showing signs of being burned themselves, only the board. It makes me wonder if they have been changed already.

Could the scenerio possibly be that since the original half recap was done, leaving a bad one still in, this caused the diodes to overheat then blowing the main fuse before the diodes could get toasted???

[tom66]

Re: Philips 42pfl5432d backlight

That's not too badly done. Caps are good Chemicon KY. The other Capxon isn't bulging so technically the repair is complete -- customer bonus (assuming a TV tech did it) to have the other one replaced I guess.

There's too much flux there (just clean it off with some IPA), and they've probably used a 1N400x instead of a TVS, but find the right parts (Page 52 of SM: http://www.tgohome.com/ServiceManual...&Search=Submit) and you should be golden.

[Dgtech]

Re: Philips 42pfl5432d backlight

Thanks Tom for the help.

The parts list only shows "Trans Suppr 120V 5W" for both zenor diodes (ZD902 and ZD904).
My two questions are:

1. What are replacements for these?

2. What would be possible causes for these to heat up?

By the way, I checked the resistor and it's fine. Schematic shows that it's a 1K ohm and it reads 1K in circuit.

[tom66]

Re: Philips 42pfl5432d backlight

1. What are replacements for these?
Any 120V TVS. e.g.
http://www.digikey.com/product-detai...ACT-ND/2770379

2. What would be possible causes for these to heat up?
Bad caps, inadequate design, take your pick.

[Dgtech]

Re: Philips 42pfl5432d backlight

Thanks, I just placed the order. I had to get some more solder wick too so that helped.

[Dgtech]

Re: Philips 42pfl5432d backlight

Well, just to update my progress... I have replaced:

C955 - crapxon
ZD902 - not bad - got hot
ZD904 - not bad - got hot
Q902 - Shorted
Fuse - Blown 5A - Still looking for a replacement. I know I have one on hand.

Once I get the fuse, I will test it. I hope nothing else is blown on this board.

[tom66]

Re: Philips 42pfl5432d backlight

Use a lightbulb in series for testing to avoid blowing more parts.

[Dgtech]

Re: Philips 42pfl5432d backlight

I forgot to update this. The TV worked after I replaced the parts listed above. This will be a birthday gift for my dad. Sucks that I cant find a remote though.