pn50b450b1d No Power

[Hiatsu2k8]

Hi and thanks for looking!

I believe I've determined the problem but wanted to run it by you guys to see if I'm correct.

I have a pn50b450b1d that doesn't turn on. It's the classic clicking issue that a lot of plasmas have. I will upload images but there are no visably damaged capacitors. VA should be 55 and vs should be 209. When I plug in I get nothing close to those to values. A small spike and then nothing. When I unplug both the X and Y board from main I get the correct values immediately at power on but then they slow drop off to 0. I tried checking the values on the X and Y board themselves but nothing is correct. I removed the power board and used an ESR meter to start checking capacitors. It's the blue esr meter I built and calibrated it myself and it works well. Some of the capacitors have much higher readings then they should. I'm assuming that the power board is bad. Is there anything else I should do to make sure?

Thanks!

[Hamie]

Re: pn50b450b1d No Power

Your power supply is probably OK.
The voltages only come up briefly on this model if you have the x and y unplugged.

[Hamie]

Re: pn50b450b1d No Power

On the y-sustain look at the input from the power supply and see if the vs pin is shorted to ground.

[Hiatsu2k8]

Re: pn50b450b1d No Power

On the y-sustain look at the input from the power supply and see if the vs pin is shorted to ground.

Pin 5 and 6 are both VS, I'm assuming the black wire is the ground. Is that what you mean by short to ground?

[Alastair E]

Re: pn50b450b1d No Power

Probably IGBT's on the Y-SUS S/C. Very rarely caps on PSU with this series.

[Hiatsu2k8]

Re: pn50b450b1d No Power

Probably IGBT's on the Y-SUS S/C. Very rarely caps on PSU with this series.

What are igbt? I'm interested in learning how to isolate the problem. I should have all the tools to diagnose. Thanks

[Hamie]

Re: pn50b450b1d No Power

Upload a photo of the top and bottom side of the y-sus.

Did you confirm that vs input is shorted to ground?

[Hiatsu2k8]

Re: pn50b450b1d No Power

Upload a photo of the top and bottom side of the y-sus.

Did you confirm that vs input is shorted to ground?

No, I did not. I apologize, I'm not familiar with how to do that. If you could please explain I'm sure I will catch on quick though. The pictures are attached.

[Hiatsu2k8]

Re: pn50b450b1d No Power

Upload a photo of the top and bottom side of the y-sus.

Did you confirm that vs input is shorted to ground?

By using a multimeter in ohms mode test both VS pins 5 and 6 and it read 0000. No short to ground, is that correct?

[Alastair E]

Re: pn50b450b1d No Power

Reads 000 then short, read OL = open.

Should equip yourself with at least a bit of knowledge of how to use your own multimeter before delving into a complicated and potentially lethal machine like a TV Set!!

Sorry, but--I'm Out!

[Hiatsu2k8]

Re: pn50b450b1d No Power

Reads 000 then short, read OL = open.

Should equip yourself with at least a bit of knowledge of how to use your own multimeter before delving into a complicated and potentially lethal machine like a TV Set!!

Sorry, but--I'm Out!

I'm trying to learn, that's why I'm here. The VS input is shorted to ground. Is there anything else you can help me with?

[mmartell]

Re: pn50b450b1d No Power

With multimeter in ohms mode put one probe on pin 5 OR 6 and the other probe on one of the screws holding down the board (ground) Make sure the tv is OFF. What is the measurement ?

[Hiatsu2k8]

Re: pn50b450b1d No Power

With multimeter in ohms mode put one probe on pin 5 OR 6 and the other probe on one of the screws holding down the board (ground) Make sure the tv is OFF. What is the measurement ?

Thanks for your help. With one probe on either pin 5 or 6 and the other probe on a ground screw I get OL.

[mmartell]

Re: pn50b450b1d No Power

Redo the test using the OUTER pins one at a time with a ground screw then test each pin together. So three tests, report back.

[Hiatsu2k8]

Re: pn50b450b1d No Power

Redo the test using the OUTER pins one at a time with a ground screw then test each pin together. So three tests, report back.

Hi, so I was confused, you said three tests but to test each pin together. Is it possible to explain what I should be getting and why? I wanted to be thorough so I tested EACH pin together and here are my results:

To Ground;
Pin 1: 20< (the reading kept increasing starting below 10 so I stopped after 20
Pin 2: 1.8
Pin 3: 13.23
Pin 4: 1.9
Pin 5: OL
Pin 6: OL

To Each Pin:

Pins Pin 1 Pin 2 Pin 3 Pin 4 Pin 5 Pin 6
Pin 1 x 21.81 0.719 0.7 OL OL
Pin 2 x x 12.22 0 OL OL
Pin 3 x x x 12.58 OL OL
Pin 4 x x x x OL OL
Pin 5 x x x x x 0
Pin 6 x x x x x x

In case the table doesn't come through I also attached the xls file. Thanks again for your help.

[mmartell]

Re: pn50b450b1d No Power

Oi my mistake here. That test is useless if the fuse is blown. One meter probe to ground the other probe on the far side of the fuse. If you're not sure which side I'm talking about try them both. I'm betting you will have a very low resistance reading on one of them.

[Hiatsu2k8]

Re: pn50b450b1d No Power

Oi my mistake here. That test is useless if the fuse is blown. One meter probe to ground the other probe on the far side of the fuse. If you're not sure which side I'm talking about try them both. I'm betting you will have a very low resistance reading on one of them.

I don't see a fuse on this board.

[mmartell]

Re: pn50b450b1d No Power

Does your meter have a "Continuity" mode ? You don't want any beeps between a power source and ground because that means you have a short circuit = bad. By what you're reporting here you don't have a short on VS on the Y board but your Va line is suspect. Remove the connector from the X board and check for a short there.

You need to do a little reading I think to get yourself familiarized with some of the working concepts here.

[Hiatsu2k8]

Re: pn50b450b1d No Power

Does your meter have a "Continuity" mode ? You don't want any beeps between a power source and ground because that means you have a short circuit = bad. By what you're reporting here you don't have a short on VS on the Y board but your Va line is suspect. Remove the connector from the X board and check for a short there.

You need to do a little reading I think to get yourself familiarized with some of the working concepts here.

You're right I definitely do. I'm having a hard time wrapping my head around some concepts though. If you're not out of patience yet I think I figured it out. For instance I tested the vs on the x board and it did beep. This would indicate a short or no resistance or short Circuit which might be why the tv isn't turning on to prevent a dangerous situation. However on VA on the y board there is no beep but also no resistance. Could that indicate an open Circuit on that board?

[mmartell]

Re: pn50b450b1d No Power

It could but it's not important at the moment. If you leave the X board unplugged and plug the Y board back in does the tv start normally ?