philips 42pfl5432d got sound no backlight

[allsmith]

Hello all! hope everbody is doing good!!Im pretty new to electronics here so i hope you all can bear with me! I would greatly appreciate your expertise!!!I recently got bit by the vintage audio bug!! and have been interested in learning how to restore/repair/recap audio receivers!! Ive been wearing out old google here lately learning everything i can on the subject and tools. I have purchased a weller wes51 iron and have been practicing soldering and testing components from electronics i pick up cheap at a local recycling center.Finding soldering and desoldering with my weller with good wick and kester solder is going pretty good! While trying to learn everthing i can about receivers and recapping, my friend brought out a couple lcd tvs with bad caps in power supply,got those up and running with just replacing the obvious swollen caps.Then i found this tv for sale not working so i picked it up for myself to replace my hd crt tv. Ok so on to my question.......

philips 42pfl5432d... here are the symptoms.....

Plug in tv,power light turns red...push power button, led turns solid green.No backlight or backlight flash.
Hooked up dvd player, tv has sound,tried to see if there is a picture with bright flashlight but i cant see no picture,not sure if my flashlight bright enough for that test or not?
push power button to turn off and led goes out, no led light at all.
push power button again,get sound and green solid led again.
power button only turns red when unit is first plugged in.
No unusual sounds.

Visual inspection...
Removed back of tv,first thing i see is sombody has already replaced the 4 bigger caps that are known for failing.
There solder job was terrible!!!
Caps they used where physically to big,with wider pin spacing,but he got them in there!
I have downloaded the service manual and there temp /capacitance/voltage is correct,and he got the polarity correct.
But i believe they are just general usage capacitors!
They are illinois capacitor ckh series.
So i decide to desolder them to resolder them and find out he damaged the pcb pads on a few of them!!!
I scrapped back the solder mask around a couple pads to get more area to solder to, and i tinned the copper and got them soldered in pretty good.

Put power supply back in tv,Same sypmtoms as before,no backlight,with sound..

Now i have read just about everthing about this model on here and have seen where some ppl have shorted diodes,mosfets and rectifiers.

I have read how to test them componets with a dmm in and out of circuit,and have tested 2 mosfets for shorts,test ok, tested bridge rectifier in circuit,test ok, tested another rectifier out of circuit,test ok.
tested a bunch of diodes in circuit and most tested ok,pulled one lead of the couple that test funny and they tested fine out of circuit.

One question i had was those general purpose caps ,will they at least make the tv work? I have no problem replacing them and the other smaller caps on ps board with the correct good quality ones that are low esr,once i know the set has a good picture!

Voltage test...
I installed the power supply back in tv,and with help from the service manual i tested voltage at the output of the power supply with the inverters and main board connected..tv plugged in and turned on..

Im getting 24v going out to the inverters
Im getting 24 and 12v going out to main board
I didnt check standby power as the service manual does not state the voltage.
I will post a pic of the pinouts and voltages.

So here is where im at, the power supply seems to be working.
I ohmed out the three tiny fuses on the master inverter board,All tested good at 0.6 ohms.
I can only find two fuses on the slave board and they test good.

So do you all think i have inverter problems or is the main board not telling the inverters to come on??

I dont know how to test inverters and have done nothing in the main board and i have seen many ppl with the same set have puffed caps in the main board,mine all look fine!

Any help would be greatly appreciated!!! and can post any pics that you all request,just wanted to get this thread started for now! thanks all!!

[allsmith]

Re: philips 42pfl5432d got sound no backlight

Couple other things i noticed are the two connectors that go to the inverters can be connected to either location on the power supply.
when i got tv i marked them so i got them in the right port,but did the original owner get them right??? Looking at the pin out pic from service manual looks to me like it wouldnt matter which port they would go to,but im not gonna try switching them! dont wanna mess something up!!

Also the rubycon caps on master inverter board looks like they been running hot around there solder connection.

And just so everbody knows there is a slave board on right hand side of tv not pictured yet. Thanks all!!!

[tom66]

Re: philips 42pfl5432d got sound no backlight

The fuses marked 4A/160V, are they good? How are you testing them?

[allsmith]

Re: philips 42pfl5432d got sound no backlight

The fuses marked 4A/160V, are they good? How are you testing them?

I tested them with dmm set to 200 ohm setting,all 4 are reading 0.6 ohm in circuit. would they need to be out of circuit to test? Thanks!

[tom66]

Re: philips 42pfl5432d got sound no backlight

They are probably fine; but another check you can do is to see if you have 24V on both ends relative to ground.

[allsmith]

Re: philips 42pfl5432d got sound no backlight

They are probably fine; but another check you can do is to see if you have 24V on both ends relative to ground.

Yes i have 24v on both sides of both fuses on the master inverter board, should i and can i do the same test on the slave board fuses? Also there is one more fuse on master board.its a 15a 76 v tested 0.6 ohms meter set to 200 ohms in circuit. Its tiny!!

[retiredcaps]

Re: philips 42pfl5432d got sound no backlight

Im pretty new to electronics here so i hope you all can bear with me!

For someone new to electronics, you sure have done a lot of homework so I commend you for that.

On the inverter board, pin 14 is BLON. BLON (backlight on) is usually originated/generated by the main/logic board to tell the inverter to turn on the backlights.

What is the DC voltage on this pin?

[allsmith]

Re: philips 42pfl5432d got sound no backlight

For someone new to electronics, you sure have done a lot of homework so I commend you for that.

On the inverter board, pin 14 is BLON. BLON (backlight on) is usually originated/generated by the main/logic board to tell the inverter to turn on the backlights.

What is the DC voltage on this pin?

Thanks i appreciate that!!! Yeah im a big research freak,I spent many hrs night before last on this web site reading everything i could on this model and all the information you and other members gave to help other ppl with there tvs. I greatly appreciate your help!

Ok pin 14 blon im getting 3.3 v
Also just a observation, i can hear a very quiet click when i push the power button on the tv.not sure where it comes from, but very quiet!

[retiredcaps]

Re: philips 42pfl5432d got sound no backlight

Ok pin 14 blon im getting 3.3 v

Most electronics follows the convention of high/low with low being 0V and high being something else.

So let's assume that BLON is ON because 3.3V is being sent by the main board.

So if you have no backlight and all the fuses and voltages are good, then I suggest looking at the mosfets.

1) Test all the P3004ND5G (Q17 is one example) on both inverter boards to see if they are shorted. See datasheet below for pinouts. There are two sources, drains and gates in this one package.



You should have 6 readings per P3004ND5G. Report them like the example in section 2 below

https://www.badcaps.net/forum/showpo...4&postcount=19

2) What is the part number of the inverter transformer? There are 20 of them on each board. They should all be the same part number.

[allsmith]

Re: philips 42pfl5432d got sound no backlight

Most electronics follows the convention of high/low with low being 0V and high being something else.

So let's assume that BLON is ON because 3.3V is being sent by the main board.

So if you have no backlight and all the fuses and voltages are good, then I suggest looking at the mosfets.

1) Test all the P3004ND5G (Q17 is one example) on both inverter boards to see if they are shorted. See datasheet below for pinouts. There are two sources, drains and gates in this one package.



You should have 6 readings per P3004ND5G. Report them like the example in section 2 below

https://www.badcaps.net/forum/showpo...4&postcount=19

2) What is the part number of the inverter transformer? There are 20 of them on each board. They should all be the same part number.

OK i checked the 4 mosfets on each inverter board doing it the way you suggested in your tutorial, 6 tests on each mosfet with dmm set on 200 ohm
I went off the data sheet you found for me for the pinouts
All combinations measure 1 or OL, my meter uses 1
Now I do get that quick flash of a number before the meter settles on 1
Am i correct that the number that flashes real fast is not the number im looking for? But what it settles on is?
I took a pic of the inverter part # for you,should be able to read it well.
I double checked that i have 24v on each side of the 4 bigger fuses on both inverter board, but have only ohm checked the tiny 3rd fuse on the master board,it ohmed out at 0.6 meter set to 200 ohm
Kinda scares me to see if there is voltage on it pins because it is so small i dont wanna bridge and cause a short!
I very much appreciate your help!
Do you think the 3.3 v on blon is not enough voltage to trigger the inverters?
I will look at the service manual again and see if it shows a voltage,but i dont think it did.

[allsmith]

Re: philips 42pfl5432d got sound no backlight

Looking at the service manual for the inverter on/off
What do you make of it for voltages?
I see 3v3 not sure what that means?

[retiredcaps]

Re: philips 42pfl5432d got sound no backlight

Now I do get that quick flash of a number before the meter settles on 1
Am i correct that the number that flashes real fast is not the number im looking for? But what it settles on is?

Some multimeters take and update only 2 readings/sec. In addition, some are quite slow at taking readings. So it is the number that it settles on that is important.

I took a pic of the inverter part # for you,should be able to read it well.

Refer to

http://www.lcdparts.net/TransformerD...ProductID=2816

For each inverter transformer on each board, measure the resistance between S1 and S2. They should all be around 1000 ohms. Report all your readings for above like so

T1
S1-S2 = 1001 ohm

T2
S1-S2 = 1004 ohm

[retiredcaps]

Re: philips 42pfl5432d got sound no backlight

Looking at the service manual for the inverter on/off
What do you make of it for voltages?
I see 3v3 not sure what that means?

Hmm,

According to the screenshot, it says

Inverter on: Low
Inverter off: High

Normally, "Low" means 0.0V and "High" is 3.3V.

That means the main board isn't toggling BLON from 3.3V to 0.0V.

PS. 3V3 means 3.3V.

[retiredcaps]

Re: philips 42pfl5432d got sound no backlight

1) Can you post a clear focused shot of the main board?

2) Can you post a clear focused close up of the area where Q850 is?

[allsmith]

Re: philips 42pfl5432d got sound no backlight

1) Can you post a clear focused shot of the main board?

2) Can you post a clear focused close up of the area where Q850 is?

Trying out a new camera,hope this aint too bad.I dont want my picture file too large,so im trying turn down the camera and still get a decent pic.

ok yeah i noticed that about high being off and low being on.
I cant seem to find Q850 yet on board even with magnifing glass.
ill see if i can find it on service manual,or if you can point it out ill get a close up pic.

[allsmith]

Re: philips 42pfl5432d got sound no backlight

Sorry still cant find Q850 anywhere,and ive looked on all boards..but i did ohm out the inverters.

Inverter transformers are all testing out at very close to 2000 ohms,
The pic of the inverter you found for me is pictured upside down,so im pretty sure im testing s1-s2.
ill keep tring to find Q850! thanks!!

[retiredcaps]

Re: philips 42pfl5432d got sound no backlight

Trying out a new camera,hope this aint too bad.I dont want my picture file too large,so im trying turn down the camera and still get a decent pic.

Do this. Trace the BLON from the inverter board back to the main/logic board. Post a picture of the main board BLON and its surrounding area (maybe a 6 x 6 inch area around the BLON).

[retiredcaps]

Re: philips 42pfl5432d got sound no backlight

Inverter transformers are all testing out at very close to 2000 ohms,

Post all your readings. The readings should all be within 3% of each other. "Very close" is very imprecise.

[retiredcaps]

Re: philips 42pfl5432d got sound no backlight

Sorry still cant find Q850 anywhere,

Did you look at the backside too?

[budm]

Re: philips 42pfl5432d got sound no backlight

OK, I look at the INVERTER ON/OFF picture in post11, you do have BL_ON (>3.3V = ON) signal correctly feeding your inverter board, please see my explanation in the picture.