Help Testing if LED TV Power Board is Functional

[aminemarref]

Hello,

My Android LED TV seems to have died last night. I wanted to do some troubleshooting myself to see if I can pinpoint the problem before calling a professional.

So, my first step was to try to see if the power board works fine; and after sifting through few online video tutorials, I did the following. I powered-on the TV, and started testing - using a handheld multimeter - the output pins of the power board (those that feed the cable that goes to the motherboard) to see if they give the expected voltages. Since this part is the so-called "cold" area of the board, I put the black probe in one of the screw holes in the chassis, and used the red probe on the pins.

A snapshot of the pinout of the board is shown in page 3 of the attached document. There are 14 pins in total, and the pinout does not seem to show every pin individually, I guess some pins are grouped together in the pinout.

Only pin 4 in the top row (counting from bottom of picture) reads 4.9V. The rest are zeros.

My question is: am I testing this correctly? Do I need to short a couple of pins or something? The reason I am asking this is that I found in certain tutorial videos that some power-board models require shorting of pins.

Please let me know if my testing is correct.

The attached document contains the model number of the board, a picture of the board, a snapshot of the pinout from the board, and a circuit diagram that I salvaged from the web.

Thanks.

 

[Nigel Goodwin]

The only supply running will be the standby 5.1V, unless the set is fully running - as the rest of the PSU is turned ON by the micro in the TV.

I would suggest that PS_ON needs to go high (5.1V) to turn the rest of the supplies ON, there's also over current and over voltage protection provided by V951/V954. However, simply sticking a piece of wire from 5.1V to PS_ON 'might' not be a good idea, as we've no idea what's connected to the other end.

It might be safer to monitor the voltage on PS_ON and see if it attempts to go high at all.

Assuming the PSU is faulty, and standby 5.1V is working, then I would expect there to be some error indication (flashing LED) telling you what's wrong.

What make and model is the TV?.

 

[aminemarref]

The TV is a no name really, it is sold in my country as brand ENIE, but a quick search in the Internet shows that its original brand is KONKA. It worked great for five years.

The TV indicator light is a steady green, does not flash at all, and even when I attempt to switch the TV off using the remote or the on-TV keypad, the indicator light does not go to red as it usually does. It stays green and the TV shows no picture or sound. The only way to switch it off is from the ON/OFF switch or by yanking the power cord.

 

[Nigel Goodwin]

Check for a voltage on PS_ON then, I presume Green means the set is turned ON, so PS_ON should be high.

 

[aminemarref]

I will do that. Can you work out which pin is PS_ON from the pinout? I am assuming - by looking at the board's picture in the attachment - that PS_ON is the pin at the top, and since there are two at the top (one from each of the two 7-pin rows), it is the one to the back.

 

[Nigel Goodwin]

Pin 7 has 5.1V on it, locate that one and work from there.