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)
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.
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.
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.
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?
You stated --
and the bottom ic on the y buffer has popped
Why do you think that popped.
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.
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.
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.
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.
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.