Philips 22pfl4507 No Power

[pauldow]

Hi,

Today's project is this Philips television. No backlight, no LEDs, no sounds out of it.

Found a blown fuse. Replaced it, and it blew right away.

I found the thread:
https://www.badcaps.net/forum/showthread.php?t=24681
which is about a 22PFL3505D

That one had a bad diode. I found a shorted 36V Zener diode.1ZB36. It's located just behind (out of sight) that small heat sink on the photo. The reverse side photo has the location circled.

Since it looks like I can't get this locally, I was wondering if there's any other components I should check before placing an order. I see there are some items on eBay that have a repair kit for this power supply with 7 components.

That semiconductor on the heat sink is a TK5A50D switching regulator, and the transistor above the 1W resistor says 208 C3203 Y

Thanks for any help

[budm]

Re: Philips 22pfl4507 No Power

Did you test that Zener diode off the board? That diode may be connected in parallel with >1 Ohms resistor.

[pauldow]

Re: Philips 22pfl4507 No Power

Yes I did remove it.

On my meter's diode setting, it's showing 0.005V in both directions.

I put it on the resistance scale, and it reads 2.6 ohms in both directions.

[CapLeaker]

Re: Philips 22pfl4507 No Power

Did you check the other diodes and the mosfet for short?

[budm]

Re: Philips 22pfl4507 No Power

Did you check the power MOSFET mounted on the heatsink for shorted Source to Drain pin?
This one of those cheaply made two-Transistors switching power supply that usually take out the MOSFET, the OPTO, the diodes, etc. when the diode in the secondary side shorted out or due to shorted load.

[pauldow]

Re: Philips 22pfl4507 No Power

The 4 rectifier diodes, and the one mounted diagonally just to the left of the MOSFET checked out OK.

I pulled out the K5A500, and I get .4 ohms from the source to drain. (My ohmmeter has .2 ohms showing when I touch the leads.) So it looks like that one is shorted.
I now see that 0.68 ohm resistor is open too.

It looks like the easiest way to fix this is to order the repair kit.

Thanks for pointing me in the (hopefully) right direction.
I'll post back here when I get the parts changed.

[CapLeaker]

Re: Philips 22pfl4507 No Power

it would have surprised me if only that zener would be gone.
check that diode left to the mosfet and check that small transitor right above the green resistor too.

[budm]

Re: Philips 22pfl4507 No Power

You are going to be replacing lots of parts in this board.
How about the diodes in the secondary side, the opto-isolator, etc.

[pauldow]

Re: Philips 22pfl4507 No Power

Sorry for the delay getting back to you.
You guys are right. So far I found a transistor, resistor, the optocoupler and three diodes are bad.

Unfortunately the repair part kit is already on its way to me. It's looking like it would be a lot easier to just replace the board for about $35, although replacing components does give me a better feeling.

[CapLeaker]

Re: Philips 22pfl4507 No Power

I am hoping the repair kit does have all of these parts you are going to need.

[Andrew F. Ali]

Re: Philips 22pfl4507 No Power

If the repair kit is on its way then wait and change out the components. Try it and if it works smile. If it doesn't...no...don't cry. Order a new board. I recommend ShopJimmy as They are to me the easiest and most reliable source for replacement boards.

[pauldow]

Re: Philips 22pfl4507 No Power

Well I got the repair kit this afternoon, and replaced all the components it came with. Even the ones that I thought were probably good.

(It did come from Jimmy.) For future reference, it's their part number 267074.

The attached photos show what I replaced. Budm was right in that there were quite a few parts that needed to be changed out.

Got it back together, and it works. The landfill will have to wait a bit longer before it gets this one.

I had thought the opto isolator and that diode circled on the Cold side were bad, but they weren't included in the kit. Since the TV works, they must be OK.

Thanks everyone for the direction on this,
Paul