Panasonic TCP50S30, Solid Red LED, LOUD BUZZING

[Truncatedhose]

Hello everyone!

So, this TV has no blinking LED, but rather it is solid red (and holding the power button down doesn't change that). The screen doesn't flash or anything; the screen is totally dead. There is a loud buzzing, which is much louder than any normal operational buzz; it sounds like when you have a crack in the plasma panel, but lots of close inspection has revealed no damage or cracks/defects in panel. I then treated all the ground points and replaced the screws (since this is a model that has that issue (and yes, some of them were slightly carbon scored), but it changed nothing.

Despite being worried that the panel may have failed and shows no signs, I proceeded with troubleshooting. See attached screenshot of service manual for troubleshooting "no picture". It says to look for the LEDs on the SC and SS boards and if they are unlit, replace either board. Sure enough, the SS board LED was not lit, but the SC was. I replaced the SS board, but still have the solid red LED and no picture still and the loud buzzing continues. I have let it run for no more than 20-30 seconds and the SS board LED stays lit. The service manual says if both LEDs on the SC and SS boards are lit, to then replace the A board, but I'm dubious.

Any thoughts or help would be greatly appreciated!

[Moreno83]

Re: Panasonic TCP50S30, Solid Red LED, LOUD BUZZING

I worked on a similar model , the 42inch version. It also had a loud buzzing sound but showed a picture. It was in someone's shop so i only temporary worked with the tv before i left the shop.

I reflowed all the solder pads on the backside of the SC/SS boards and used lock washer screws. The buzzing was still there but not as loud as before.
When i applied pressure on the SS board ( Top side ) the buzzing changed a bit. I got a feeling the SS board is the problem on these models for the buzzing sound.

Does the tv respond to the remote? I know you don't get a picture but it might respond to the remote.
Contrast set to high also makes the same panel buzzing sound because the panel has to work harder. Customer had it set to dynamic + contrast set to full.

The sound probably comes from the transformers on the power supply? Don't worry , thats not your problem because i also replaced the power supply on the model i worked on and that did not change a thing. Only thing i didn't do was replacing the SS board. You already replaced the SS board so i think you got a panel problem.

What happens if you remove the buffer boards? Use SC50 jumper.

[Moreno83]

Re: Panasonic TCP50S30, Solid Red LED, LOUD BUZZING

Ps , are the Vsus voltages ok? Must be 215V on this model. ( Out of my head... )

[Truncatedhose]

Re: Panasonic TCP50S30, Solid Red LED, LOUD BUZZING

I worked on a similar model , the 42inch version. It also had a loud buzzing sound but showed a picture. It was in someone's shop so i only temporary worked with the tv before i left the shop.

I reflowed all the solder pads on the backside of the SC/SS boards and used lock washer screws. The buzzing was still there but not as loud as before.
When i applied pressure on the SS board ( Top side ) the buzzing changed a bit. I got a feeling the SS board is the problem on these models for the buzzing sound.

Does the tv respond to the remote? I know you don't get a picture but it might respond to the remote.
Contrast set to high also makes the same panel buzzing sound because the panel has to work harder. Customer had it set to dynamic + contrast set to full.

The sound probably comes from the transformers on the power supply? Don't worry , thats not your problem because i also replaced the power supply on the model i worked on and that did not change a thing. Only thing i didn't do was replacing the SS board. You already replaced the SS board so i think you got a panel problem.

What happens if you remove the buffer boards? Use SC50 jumper.

Thanks for your reply! I know what you're talking about regarding the buzzing with the bad ground points and high contrast and so forth. Like I said, I fixed all the grounds and replaced the screws with the updated Panasonic ones and it changed nothing. Also, this buzzing is not the same as the kind of buzzing you're talking about. This is MUCH louder and it's coming from the panel itself, not any board or transformers on boards.

I checked the VSUS: it is 215v. Yes, the TV responds to the remote; all I can really try is the power button, right? (since the screen is off) But yes, it turns on and off with the remote. I removed the buffers and jumped SC50 and the symptom and buzz are exactly the same. So you think it's the panel that is bad? And the SS board had failed, but possibly due to the panel or...?

[Moreno83]

Re: Panasonic TCP50S30, Solid Red LED, LOUD BUZZING

I think the panel is dead. It does not have to be the front of the panel that has the cracks , can be the back of the panel.

I would remove the boards and check the screwholes. Is this your own tv or customer tv? Do you know the history of the tv?

It can be that someone used too long screws and damaged the panel from the inside. I've seen this before. The panel is real close to the screw holes. 1 / 2 mm longer screws then the original and your touching the panel.

[Truncatedhose]

Re: Panasonic TCP50S30, Solid Red LED, LOUD BUZZING

I think the panel is dead. It does not have to be the front of the panel that has the cracks , can be the back of the panel.

I would remove the boards and check the screwholes. Is this your own tv or customer tv? Do you know the history of the tv?

It can be that someone used too long screws and damaged the panel from the inside. I've seen this before. The panel is real close to the screw holes. 1 / 2 mm longer screws then the original and your touching the panel.

It is a customer TV. It doesn't look like it has been worked on before. The screws that were in it were long. Thanks for your input and ideas.

I'm hoping someone out there has some kind of test to verify a dead panel...?

[Moreno83]

Re: Panasonic TCP50S30, Solid Red LED, LOUD BUZZING

Think you already tried everything! You got a working powersupply , sc board ,ss board.

You could test the buffer boards for shorts but they would have shut the set down with a sos blink code.

Only thing i can think of is the a board that might have failed showing no picture BUT the panel is making noise , personally i think someone used to long screws and damaged the panel from the inside.

Why? Becaused it happened to me! I repaired a sc board and from all the screws 1 was a little longer and i damaged the panel from the inside. The set worked but the next day the panel made a loud buzzing noise because all the gasses were gone. Nothing to see from the outside but a small scratch on the inside.

Sorry but i think you wont be able to repair this tv!

[Truncatedhose]

Re: Panasonic TCP50S30, Solid Red LED, LOUD BUZZING

Think you already tried everything! You got a working powersupply , sc board ,ss board.

You could test the buffer boards for shorts but they would have shut the set down with a sos blink code.

Only thing i can think of is the a board that might have failed showing no picture BUT the panel is making noise , personally i think someone used to long screws and damaged the panel from the inside.

Why? Becaused it happened to me! I repaired a sc board and from all the screws 1 was a little longer and i damaged the panel from the inside. The set worked but the next day the panel made a loud buzzing noise because all the gasses were gone. Nothing to see from the outside but a small scratch on the inside.

Sorry but i think you wont be able to repair this tv!

Thank you again. I scrapped it.