Help with 42PFL5432D/37

[burner6999]

Ok so here is the run down. I have picture but no backlight. I got the tv with a blown fuse. When I put a new fuse in it, it blew resistor R963 (red in first pic). After replacing that I checked some diodes and found 1 bad at D912 (in blue in first pic). Then I tested the mosfets mark in red and blue in second pic and found them bad and replaced them. Now when the tv is on I get picture but no backlight. The other thing is that I only get 1.5v DC at the invertor boards. So I was wondering if you guys think buying a working power supply will fix all problems? I can get 1 for $78 but dont want to waste the money if there is another problem. Please let me know what to check. All of the caps look fine on main and power board.

[JimmysTGP]

I think the TV was hit by lightning or some type of power surge, me personally I don't continue working on sets that were damage under these conditions. What may happen is you may fix the TV but all the rest of the parts have taken some of the surge. But on the bright side is that you may fix the set and you will have a good working set. Good luck with this.

[burner6999]

My thing is if it was more than just the power supply then I should be getting 24V to the inverter boards.

[JimmysTGP]

It won't hurt to getting another PS, I don't know what your budget is, however if buying the PS for cheap could atleast answer more to what other problems the set may have, maybe the direction you may want to go.

[senndogg]

for a successful repair i think you should replace the major part of components in that PSU. you should start from the TEA1507P, the transistor(s), diodes and resistors. altogether components should be under 20$. and the most important thing; you'll enjoy every bit of your work.
if you dont succeed thant try plan B: getting a new PSU.

[senndogg]

i see, your problem is in the 24V section. if you manage to inject 24V in the inverter red and black cables you can test the TV and look for other problems.

[burner6999]

How would I go about doing that? Also would not getting 24v to the inverter cause the backlight not to come on?

[budm]

The 24V from the power supply AND the BL_ON command from the main board are needed for the backlights inverter board to lght up the lamps, the tow MOSFET's: One is for the PFC circuits, and another one is for the 24V power supply section.
If you check the the DC voltage on that large 450V cap when the tV is on and you do get around 400VDC on that cap, it means the PFC is working, then you may have bad SMPS IC or other components that were damaged when the MOSFET went out. iT depends on haw far in troubleshooting down to component level you willing to do.
By, do you get 24VDC if you disconnect the cables to the Inverter board, since if the inverter boards draw too much current, it will shutdown the 24V power supply to protect itself.

[tom66]

I wouldn't rule a smoking resistor as lightning/surge damage.

Very strange that I've -never- encountered a piece of surge damaged electronics here in the UK. Why is it so common in US?

My immediate guess would be a failed FET possible due to the power supply controller becoming unstable due to bad caps, very common on this Philips/Magnavox chassis.

[senndogg]

i have seen so many, and believe me Tom, it goes far than the main transistor. almost everything in the primary section has to be replaced.

[burner6999]

I checked the PSU with the inverter boards unplugged and I only got 2.33VDC. So I am guessing there is a problem with the power supply. I went ahead and ordered one. I will post back and let you know what happens.

[burner6999]

Thanks for all the help guys. I got the new power supply and it is working great.

[budm]

Great news! good job.

[burner6999]

Thanks man.