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TV Tech1
TV Tech1, Technician
Category: TV
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Experience:  30 Years experience. Authorized Warranty servicer.
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My plasma tv cut out and started making a clicking noise. I

Customer Question

My plasma tv cut out and started making a clicking noise. I changed the y buffer, y main and power board after some help from a forum. My problem now is it only has sound and no picture and the bottom ic on the y buffer has popped.
Any help would be appreciated.
Submitted: 3 years ago.
Category: TV
Expert:  TV Tech1 replied 3 years ago.
You have the single buffer or dual buffer board in your TV?
Customer: replied 3 years ago.
Just 1 Y buffer board. Long skinny board on the left hand side.
Expert:  TV Tech1 replied 3 years ago.

Oh boy....and it smoked the new board's IC the moment you connected it.

 

That's NEVER good news. I've had those IC's smoke the moment I powered it on and that means your TV's plasma panel is shorted internally and that's why those ICs smoke.

 

I was hoping for a dual board setup, because a bad Upper board can smoke the lower board. Not in your situation.

 

And look at the cost of replacing your plasma panel (one of several panels used in your C450 series TV set)

 

http://www.encompassparts.com/item/8166614/Samsung/BN96-12707A/Assy_Pdp_Module_P

 

New cost versus repair cost....and they haven't charged for shipping yet (another 100 or more) and it's not cost-effective.

 

I'm sorry that I had to give you bad news, but....that's part of being a TV repairman.

 

 

Customer: replied 3 years ago.
Is there any way to check the plasma panel as I have looked for burn marks under a bright light and nothing apparent. Even with the y buffer and main disconnected I still can't get a DC reading from the power supply. Only on start up then rapidly back to 0v. Heat shrink on main video board gets pretty hot.
Expert:  TV Tech1 replied 3 years ago.

Well the smoke came out of that buffer board's ICs so you know that is delivering Excess current to the plasma panel.

 

That's why it smoked.

It sounds like you already inspected the panel with a flashlight and didn't find any cracks or Black pixels, which is what I look for too. The Video board isn't the cause, as those ICs do get pretty warm and are heat-sinked for that reason. But it's two boards away from the buffer board, so I'd expect the logic board, the Ysus board and the buffer board to exhibit a "domino effect" affecting all boards between the buffer and the video boards. I've never seen an issue like that on any flatscreen TV set.

 

 

Customer: replied 3 years ago.
Where can I start fault finding to find out where I am losing the voltage? Or why it's going into some shutdown/safety mode?
Expert:  TV Tech1 replied 3 years ago.

You would be wasting your time attempting fault-finding. The new plasma panel comes with the Buffer and Ysus and Xsus, buffers and logic boards integrated into the plasma package. That's how they sell it.

 

You just transfer your power supply and video board over to the new plasma panel.

 

The TV is going into safety shutdown simply because that buffer smoked/shorted. You can't disassemble the plasma panel so direct replacement is your only option right now.

Customer: replied 3 years ago.
The y buffer, y main and z sus are disconnected from the power supply currently so does that not suggest a fault with the video/logic board as they are the only boards being powered currently?
Expert:  TV Tech1 replied 3 years ago.

What exactly are you asking?

 

You can disconnect those boards and the TV will not stay turned on if the buffer is connected. Are you checking the boards that come with the new plasma panel?? Seeing if they can be salvaged?

 

 

 

 

Customer: replied 3 years ago.
Basically they current boards on the tv are disconnected so they can not be shutting the tv down. The video and logic board are attached. One of these boards is shutting the power supply down and I would like to know how to fault find to see which one is at fault.
Expert:  TV Tech1 replied 3 years ago.

You stated --

 

and the bottom ic on the y buffer has popped

Why do you think that popped.

 

 

Customer: replied 3 years ago.
Could it be because I didn't replace all the boards at the same time?
Expert:  TV Tech1 replied 3 years ago.

No, you replaced the buffer and it smoked. The Ysus can't smoke it only the plasma panel can. The Ysus has protection circuits that shuts it down, the buffers don't. That's why your TV turned on...the Ysus turned on....then the buffer smoked

 

Power does not flow backwards.

Customer: replied 3 years ago.
It's strange because when the other board went pop it was an ic 3 up from the bottom that popped. Could a failed part on the y sus cause it to surge the buffer and cause that to fail? Sorry for all the questions but I just can't accept the plasma has failed until I have exhausted every option. To stubborn to give in.
Expert:  TV Tech1 replied 3 years ago.

Well.....my experience has always been if the buffer smoke....it's the plasma panel. I've called Samsung about this too, and the Samsung techs have always said the same too.

 

I've cranked the power supply voltages up to their maximum and that has never done anything except reduce dots on the picture or create a white or snowy picture....none of them have ever smoked a buffer.

 

Turn down you power supply voltages if you want, get another buffer board and Ymain board if you don't believe me. But you're just throwing good money after bad.

Customer: replied 3 years ago.
That is fair enough but still doesn't explain why the power board is not showing any voltage whilst the y boards are not plugged in??
Expert:  TV Tech1 replied 3 years ago.

The power board can get damaged when the Ymain pulls too much current. More than likely the fuse and resistors opened up on the power supply. And the Y driver board gets fed Vs voltage directly from the Ymain. That's why we always check all 3 boards together.

 

 

Customer: replied 3 years ago.
I hear sound when the tv is turned on so doesn't this suggest the power board is functioning ok?
Expert:  TV Tech1 replied 3 years ago.

Your power board is a mult-stage unit. Sound works on the lower 5 and 12 volt power system, while the Ymain and the X main board are driven by the higher power 200 Volt and 80 volt supplies.

 

Those are isolated from the 12 and 5 volt supplies to protect and limit damage between the two sections and the associated electronics.

 

You wouldn't want the 200 or the 80 volts slamming into digital 5 or 12 volt sections of the TV set, causing a "domino effect" and smoking all the boards.

 

That's why you get sound, that's why your TCON is isolated and that's why they put optoisolators in between the 12/5 volt and 80/200 volt sections on both the Ymain and X main and the lower voltage sections on the power supply board. They've been doing that since the 90's. They can limit the damage to the TV set that way. The 200 volt stays in the X/Ymains....and the 12/5 stays in the Main, Tcon, Buffers, and X/Y signal creation circuits.

 

 

 

 

Customer: replied 3 years ago.
Ok how can I test to se if its the power board at fault and not the logic board?
Expert:  TV Tech1 replied 3 years ago.

Facts --

 

Your logic board's lamp light up -- it's functioning.

 

You changed the y buffer, y main and power board Even with the y buffer and main disconnected I still can't get a DC reading from the power supply. Only on start up then rapidly back to 0v

 

That indicates the power supply does turn on, but shuts down quickly to protect itself. That's because the Logic board does not like what it is reading, and the Ysus protect line is shutting down the entire system.

 

Disconnect the Ydriver from the Ysus Reconnect power to the Ysus.. Does it now stay turned on?

 

If so, the Ysus is ok.

If not, the Ysus has been damaged by the Ydriver.

 

And since the Ydriver repeatedly smoking itself....the only thing that can smoke a Ydriver would be a bad Ydriver IC or the plasma panel is eating Ydriver ICs for lunch.

 

Listen, if you REALLY don't trust the fact that you replaced the boards all at the same time, you'll want to replace the Ydriver, the Ysus, and the power supply board with new boards all at the same time. Then you can trust the boards haven't been killing each other, and if the Ydriver smokes again....then only the plasma panel is the board killer.

 

But.....this is what I do.

 

I get the Y driver disconnected from the Ymain. I connect the Power supply and Ymain together and see if it STAYS TURNED ON with no problems.

 

Then I add the Ydriver and try it again. If it stays turned on, THEN I connect the plasma panel and see if the Ydriver ICs smoke.

 

That's conclusive to me that the plasma panel is bad.

 

But you've smoked two Ydriver boards. That to me is a bad plasma panel.

 

That's just been my experience with plasma TV sets.

 

 

 

Customer: replied 3 years ago.
I have done this process and with a new power board plugged in without any y boards attached just logic and main I still can't get a steady voltage so I am certain either logic or main are at fault? I have thou roughly checked over the screen and when plugged in before it flashed white so I think it's ok. Before I put a 900 quid piece of kit in the dump I want to exhaust all possibilities.
Expert:  TV Tech1 replied 3 years ago.
So you disagree that the logic board's lamp does light up?

The main board turns on the logic board.
The logic board controls the power board. The logic board monitors the Ysus and Xsus. If they don't fire up and send its OK signal, the power will be shut off. The green light on the logic board indicates that. No green light, the logic board is presently turned off.

The main board will sit there telling the logic board to turn on all day long, but the Logic board is the master of all boards that power up the Plasma panel. It rules with absolute control.

So if you think it's a problem between the logic or the main board, do the logic board.
But as far as I'm concerned, replace the Ydriver/Ymain/Power boards if you replaced them one at a time.

And....I would lean that out even more with the Ymain and Ydriver being the only ones I'd replace if I didn't install them as a set the first time.

And...I'd take that smoking Ydriver pretty seriously.

But, you don't take me very seriously do you.


Customer: replied 3 years ago.
I was hoping as you are the expert you could take me through some fault finding instead of just saying the screen has perished. The y b
Customer: replied 3 years ago.
I was hoping as you are the expert you could take me through some fault finding instead of just saying the screen has perished. The y boards disconnected should not prevent the power supply from showing the correct voltage at the test points unless another part is faulty ie main board/logic board. I asked for help diagnosing and you haven't done that so far. For all you know I could have purchased a faulty replacement board!

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