Philips 32pfl520398 suspected TCON faulty

[newbie1]

Hi Guys,

I am working on this LCD TV

Problem : Black screen with No picture. Sound ok. Backlight is ON.

I disassembled it and suspected the TCON is faulty. TCON is V315B1-C05. Upon measuring some transistors & diodes on the TCON, I found QP1 (marked A3PA 1A) to be shorted. I removed it from the board and confirmed that indeed QP1is shorted off the board. Measuring on the same location on the board with QP1 removed shows it is not shorted. Hence, I will need to replace it but i do not know what is the exact transistor from the marking.

Hope the experts here can guide me along..
Thanks in advance.

[cashkennedy]

Re: Philips 32pfl520398 suspected TCON faulty

Generally a service a manual would be a good place to start, but this model number bring up nothing online, and the t-con is really rare. So you might want to check your model / part numbers.

[newbie1]

Re: Philips 32pfl520398 suspected TCON faulty

Thank you for your reply.

What i can search online are these :
http://www.s-manuals.com/smd/a3

However, QP = transistors isn't it?. and mine is SOT-323/SOT-23. So i am still confused.. The closest i can guess is
https://cdn.badcaps-static.com/pdfs/...0659dfcc30.pdf
But it is a RF Schottky Barrier Diodes not transistor.

[Clydeuk]

Re: Philips 32pfl520398 suspected TCON faulty

If you search A3PA it says it is an N channel enhancement mode MOSFET, though the ones I've checked are in a larger package. Looking at your T-Con suggests this is likely, I'll just check some of my old T-Con boards.

[newbie1]

Re: Philips 32pfl520398 suspected TCON faulty

WOW!. How did you came up with that dude?. Is it possible for you to give a link to the search result?. I will need to check what are the other compatible models as replacement. Thank you.

[Clydeuk]

Re: Philips 32pfl520398 suspected TCON faulty

http://www.alldatasheet.com/view.jsp...rd=A3PA-7010-2 there's a list there, I'm suspecting you have the SOT23 variant, which I haven't spotted as yet. It appears to be used in your circuit as a buck converter, to generate a low voltage high current supply. Similar circuits are used in computers for powering the processor. In your case it may be for the TFT array. Hopefully there's not a fault with that.

[Clydeuk]

Re: Philips 32pfl520398 suspected TCON faulty

Before you dive in further, I've found a T-Con with the same IC as you have there (MAX8728E), it has a similar looking circuit but the part that resembles yours has a different device. Looking at the IC datasheet may give you an idea what pin of the IC connects to that, in mine it appears to be pin 19 which looks like the supply. It could well be a double diode.

Here's the datasheet link.

[martyparish]

Re: Philips 32pfl520398 suspected TCON faulty

Edit: Sorry, I was looking at the wrong device! My bad

[newbie1]

Re: Philips 32pfl520398 suspected TCON faulty

Before you dive in further, I've found a T-Con with the same IC as you have there (MAX8728E), it has a similar looking circuit but the part that resembles yours has a different device. Looking at the IC datasheet may give you an idea what pin of the IC connects to that, in mine it appears to be pin 19 which looks like the supply. It could well be a double diode.

Here's the datasheet link.

Thanks again Clydeuk. I will check the datasheet and see which pin on the ic is the Qp01 linking to.

[newbie1]

Re: Philips 32pfl520398 suspected TCON faulty

I took another photo this time after removing QP1. From what i see it is linking to pin 27 (Gate). From the MAX8727 datasheet page 14, it should be a p-channel MOSFET.Similar to FDN304P. I hope i am reading it correctly here.

[newbie1]

Re: Philips 32pfl520398 suspected TCON faulty

Update :
Replaced the p-channel MOSFET with a FDN304P. It did not work well. End up I bought a replacement T-con & TV has been running fine so far.