Phillips LCD TV 42PFL7433D/12 weird problem

[nomrower]

Merry Chrismas and a happy new year to everyone. Im facing a strange problem with my TV. Its a Phillips TFT-LCD42PFL7433D/12.It used to work normally until the day that it started turning itself off after a long period of viewing (about 3hours). I dissasembled it and found out that the big capacitor in the center of the psu, a 330uf 200V was bulged. I thought thats the problem and after measuring the cap which showed 130uf value in my multimeter i was sure this is it. i went to my local store and found available only a 330uf 250V and though it should be fine. I went ahead and replaced it but now TV doesnt turn on at all. When i try to power it on i hear a 1 click noise from the psu the frond led flashes twice but it doesnt turn on at all. I tried to put back the old capacitor back but it still doesnt turn on. Does anyone have any idea what went wrong? I will also attach some pictures.Thanks in advance.

PSU partnumber: 310432852762
Input Voltage: 250V

[R_J]

Re: Phillips LCD TV 42PFL7433D/12 weird problem

did you put it in with the correct polarity ?

[nomrower]

Re: Phillips LCD TV 42PFL7433D/12 weird problem

Yes i definetely did. Now the old capacitor is on but TV doesnt turn on at all. Before that it used to run for about 3-4hrs shut itself down and i could turn it back on instantly. Now even with the old cap in place and nothing else touched its dead. If i did put the new cap in wrong polarity dont you think it would explode instantly?

[nomrower]

Re: Phillips LCD TV 42PFL7433D/12 weird problem

I also measured voltages comparing with this diagram and IM95 port seems fine 3.362V standby, but IM99 port doesnt have voltage at all. Is that normal on a tv on standby?

[R_J]

Re: Phillips LCD TV 42PFL7433D/12 weird problem

The 3.3 volts on pin1 of im95 is the standby voltage that is going to the main board, pin2 of im95 is the power on signal to turn on the other voltages, what is the voltage on that pin, and does it change when the power button is pressed?
And yes if the cap was in backward it would either blow the cap or the main fuse, But just chainging the cap should not have caused the power supply to stop working, It is possible there are poor solder connections somewhere on the board.

Is that 12 volt supply marked A3 on the bloack diagram a separate board?

[nomrower]

Re: Phillips LCD TV 42PFL7433D/12 weird problem

On standby voltage on pin2 is zero and when power button is pressed it goes 12v for one sec and then drops back to zero again. same thing happens also with pin1. on standby its 3.3v and when i press the power button its goes 12v for 1sec and then drops back to 3.3v.

I also didnt understand what do you mean by: "Is that 12 volt supply marked A3 on the bloack diagram a separate board?"

[nomrower]

Re: Phillips LCD TV 42PFL7433D/12 weird problem

I also checked the board with my magnifying glass at all its solder points and again everything seems normal.Should i resolder everything anyway?

[R_J]

Re: Phillips LCD TV 42PFL7433D/12 weird problem

Diagram that is in post #4 ? on page 1, it shows [A3 DC-DC] which seems to be a 12 volt supply coming from the 24 volt supply.
on page 2, 12 volts is fed to r3145 then to a number of transistors which end up connecting to base of 7126-2 transistor
If you are getting, 12 volts for a second, I suspect you are also getting +24 volts for a second
check if transistor 7140 is shorted b-e
It's a hard diagram to follow

[nomrower]

Re: Phillips LCD TV 42PFL7433D/12 weird problem

Hello again and sorry for my delays, ive been through some other problems. Anyway, i did found 7140 which is not shorted and i also checked 7126 which is also not shorted. I dont get +24v for a sec i get about +20v for i sec.

[nomrower]

Re: Phillips LCD TV 42PFL7433D/12 weird problem

I also took a picture of them and they seen both fine. nothing shorted or so.

[R_J]

Re: Phillips LCD TV 42PFL7433D/12 weird problem

Do the +VSND and -VSND voltages come up for a sec. also? There are 2 fuses, 1140 & 1141 off pins 9 & 12 of transformer 5140, are they ok.
It seems like the power supply is going into shutdown for one reason or another