Philips 42pfl5432d backlight

[ryan74]

this tv was dead when i got it and noticed bad caps so i ordered and replaced all power board caps.
now it powers on ok, no blink codes and red led turns to solid green.
backlight comes on and it starts to flicker on and off fast.
I hear squeeking from power board, sounds like its from transformer in picture.

bl_on is 3v
vbl is 17-18v seems to pulse a little with backlights flickering.

i havent downloaded a service manual yet but i assume the blv should be 24v.

it is difficult to get underneath to check voltages on transformer but i will see what i can do. if i cant get to all the leads can i remove and test it somehow? all i have is a dmm.

[Dgtech]

Re: Philips 42pfl5432d backlight

Have you checked these threads yet??

https://www.badcaps.net/forum/showth...ght=42pfl5432d

https://www.badcaps.net/forum/showth...ght=42pfl5432d


They might have already fixed this problem.

[Dgtech]

Re: Philips 42pfl5432d backlight

By the way, this guy on ebay is selling a repair kit for this TV. On his listing is a chart of all of the caps that he sells with the kit. Did you replace all of these??

http://www.ebay.com/itm/Repair-Kit-P...item35bc81656e

[ryan74]

Re: Philips 42pfl5432d backlight

thats who i ordered caps from. yes i replaced them all

i did some reading and found this:

2) Shorted Transistors/MOSFETs

On some LCD brands (example: Benq) the transistors (C5707) are sometimes shorted. Transistors are usually marked with a "Q" designation.

If you have a manual range multimeter, set it to 200 ohms (two hundred). You can test for shorted transistors "in circuit" (with power off and unplugged)

a) put black probe on pin 1 and red probe on pin 2 - read/record ohm
b) put black probe on pin 1 and red probe on pin 3 - read/record ohm
c) put black probe on pin 2 and red probe on pin 3 - read/record ohm

If any reading is less than 30 ohms you might have shorted transistor. Remove the transistor and repeat the tests out of circuit to verify.

Note: a shorted transistor would likely cause a very brief flash of the backlight or no backlight.

Mosfets

If you have a manual range multimeter, set it to 200 ohms (two hundred). This is for 3 pin ICs only. You can test a mosfet (Q, IC designation) "in circuit" by (power off and unplugged)

a) black on pin 1- red on pin 2 - record ohms
b) black on pin 1- red on pin 3 - record ohms
c) black on pin 2- red on pin 3 - record ohms

If any reading is less than 30 ohms you might have shorted mosfet. Remove from circuit and repeat the tests to verify.

Some mosfets are more than 3 pins. To test those, identify the part number and search for its datasheet. Once you find the datasheet, the pins will be designated source (S), gate (G), and drain (D). It will probably be documented as S1, S2, G1, G2, D1, D2.

Simply test

a) black on pin S1- red on pin G1 - record ohms
b) black on pin S1- red on pin D1 - record ohms
c) black on pin G1- red on pin D1 - record ohms

Repeat for the "2" pins. That is S2-G2, S2-D2, G2-D2.

Note: a shorted mosfet would likely cause a very brief flash of the backlight or no backlight.



since voltage is fine untill i plug in the inverters im going to start there

[ryan74]

Re: Philips 42pfl5432d backlight

i started testing inverter voltage at Q31
nikos
P3004ND5G
WN16J1011
P1-0.00V
P2-0.95V
P3-3.2V +/- 0.6V voltage wasnt steady

this is the spot i caused shorted
backlights stopped flickering
at the least i blew fuse F401
at this point im ready to just buy a new inverter and power supply board but im upset now.

missed ElektroTanya's registration test by 1... thought i would only get 1 right.

[Mr Bill]

Re: Philips 42pfl5432d backlight

What's the part number on the white sticker in pic #1? It'll be 27-DOXXXXX. I might have that board.

[ryan74]

Re: Philips 42pfl5432d backlight

inverter board #
27-D011811 0722SL M87511
1420H1-L301F

power board #
ADPF24300R1P
P4P773640406

when i turn it on the power board made noise(chirps) im not sure anything is wrong with it.
With inverter now dead(or when it was unplugged before) i get 24v. output to inv.

let me know otherwise i found this
http://www.shopjimmy.com/philips-996...verter-kit.htm

found this too. so i think the chirping could be zener diode and might explain the unsteady 18v i got with inverter plugged in.
http://www.ebay.com/itm/ADPF24300R1P...90737474293%26

[ryan74]

Re: Philips 42pfl5432d backlight

inverter is ok.
im going to have to order a power supply unless someone can help me fix it.
still only getting 18v to inverter and backlights flicker on and off.
chirping sound from big yellow transformer when i turn tv on.

originally it had no power and i replaced all caps from lcdalternatives on ebay.
i know i should check the mosfets, zener, and transformers but i could use help doing that.

[Mr Bill]

Re: Philips 42pfl5432d backlight

Check these 2 diodes. These 2 in the past have caused the chirping for me.

[ryan74]

Re: Philips 42pfl5432d backlight

part # LT7232
P6KE120A

ZD902- .577
.0L
ZD904- .573
.0L

Q901- W18NK802
CCIBS VW
MAR 722
black probe on p1
p1-2 = .0L
p1-3 = .0L
black probe on pin2
p2-3 = .451

Q902- W26NM60
CC127 V3
MAR 720
p1-2 = .0L
p1-3 = .0L
p2-3 = .471

i can never find data sheets for components.
is there a database or just manufacturer.

[Mr Bill]

Re: Philips 42pfl5432d backlight

ZD902 & ZD904 are good. Check the other diodes in that area and see if they read ok. Are you measuring Q901 & Q902 in the diode mode on your meter? I usually test mosfets with my meter set to OHMS, 20k range.

[ryan74]

Re: Philips 42pfl5432d backlight

i been checking them in diode mode.
im not sure how to set meter for 20k ohm
i have a klein mm1000
i can chose resistance/diode/cont. but i dont know how to set the range.
when i hit range button it switches from kohm/ mohm/ ohm

i also tried to check D922

STPS40H100CW
CCI6B VWE
MAR 722
black probe on p1
p1-2= .0L
p1-3= .0L
black probe on p2
p2-1= .238
p2-3= .238

i read that most should be .3-.8 and this seems low

[Mr Bill]

Re: Philips 42pfl5432d backlight

Just choose resistance for the mosfets. I'm thinking your meter is an auto ranging model. RetiredCaps can probably elaborate on this since he knows alot more about multimeters than i do.

The .238 is more than likely good. I've seen a few in circuit read as low as .160 but read correctly out of circuit.

[retiredcaps]

Re: Philips 42pfl5432d backlight

1) I have seen this power board/inverter combo before.

2) 18V is not enough to power the inverter board, it should be a solid steady 24V DC.

3) To test STPS40H100CW properly, set your multimeter to diode test. Refer to

https://cdn.badcaps-static.com/pdfs/...00b9cbac2c.pdf

a) Measure A1 to K1. Reverse test leads. Report both readings.
b) Measure A2 to K1. Reverse test leads. Report both readings.

4) To test a mosfet, I use a simple resistance test. If it is a 3 pin transistor, I just measure the resistance between pins 1-2, 1-3, and 2-3. Any reading less than 30 ohms suggests the component is shorted.

5) If nothing seems obviously shorted, you can try connect two 12V automotive bulbs in series to the 24V output of the power board (disconnect the inverter board). With this test, you are trying to determine if there is a short on the inverter board that is dragging down the power supply OR the power supply can't provide 24V DC reliably.

6) PS. Diode measurements are reported in volts on your multimeter.

7) I have used an equivalent to the Klein MM1000 (UEI DM393). Both are OEM from some company in Korea. The UEI DM391 fared fairly well in Dave Jones' $100 multimeter shootout (episode 99).

[ryan74]

Re: Philips 42pfl5432d backlight

I wanted to post this quik before i had a chance to test STPS40H100CW properly.(thanks for the data sheet)

I checked a bunch of diodes and they all were in range out of circuit.
a few showed 0.0v in circuit but tested fine ooc.

i was still convinced the chirp was coming from the big voltage transformer so i got out my auto stethescope and started to localize sound.
the chirp was loudest when holding scope on the outside of the big transformer so i tried taking voltage readings(i have to read how to test volt reg still).
results are on pic.

part # 80TL42T913 L
PT-007241-5
LITAI DASH2B-19

in the mean time i will go back and read how to test voltage transformer, test it, and STPS40H100CW

5) If nothing seems obviously shorted, you can try connect two 12V automotive bulbs in series to the 24V output of the power board (disconnect the inverter board). With this test, you are trying to determine if there is a short on the inverter board that is dragging down the power supply OR the power supply can't provide 24V DC reliably.

i get 24v out to inverter if inverter is disconnected(fluctuates about 1.5v)
connected it gets 17.6-18.73v
the inverter board was replaced, same symptoms with both boards

the bar graph on meter display bounces between 20-25

[selldoor]

Re: Philips 42pfl5432d backlight

Are you calling the big yellow component in the picture a voltage regulator?
It is a transformer and the out voltages dont really mean anything.

[tom66]

Re: Philips 42pfl5432d backlight

As selldoor says, it's not a voltage regulator. Have you replaced the startup cap?

[budm]

Re: Philips 42pfl5432d backlight

Is the DC voltage on that large DC filter cap steady at 390VDC since it is PFC Voltage booster circuits, this voltage is used for the 24V power supply driving circuit.
Service manual:
http://elektrotanya.com/?q=showresul...oria=&kat2=all

[ryan74]

Re: Philips 42pfl5432d backlight

lol i edited post above. i realized i was calling it a regulator.

the big cap is the startup cap right? i have not replaced it, i dont have parts around.
I dont have a way to setup board to test the big cap directly to its leads so i tested neerby and marked on pic.(335vdc) i guess it is a little low.

as for the STPS40H100CW
in circuit i got odd reading
a) a1-k1= 0.212v
k1-a1= 1.75v slow increase in voltage
b) a2-k1= 1.75v slow increase
k1-a2= 0.212v

out of circuit
a) a1-k1= 0.222v
k1-a1= .0L
b) a2-k1= 0.230v
k1-a2= .0L

i need a "power supply for dummies" to help understand better what im dealing with when i try to repair boards like this. the only replacement board i found was $100
bit by bit im trying to understand all the circuits, schem., and components but i have a long way to go.

[tom66]

Re: Philips 42pfl5432d backlight

You are in the US? 335V is fine, some PFC do not use 400V for US versions but instead a lower voltage.