I've spent about 3 days troubleshooting the main board on this TV. It's chassis number is P46841-10 and the part number for the main board is Z5WJ.
I was getting no PS_ON from the main and quickly determined that the 3.3v standby was shorted to ground. The voltage regulator for the 3.3v STBY on the analog board was getting hot so that was where I started. The regulator tested ok off the board so I removed a jumper to disconnect it from the digital main. Then I got 3.3v and it no longer got hot so I knew the problem was with the digital main board.
At this point I then located all of the components which the service manual showed were on the 3.3v stby circuit. I removed every component and all tested OK. I suspected the CPU at this point but wanted to be absolutely certain before I removed it. I then discovered that there were more components on that circuit than the service manual showed schematics for. With a lot of help from Photoshop, I traced out the 3.3v stby circuit. This was not an easy task because it's a layered board. So really I only traced out the surface paths.
In the process I determined that the 1.1v stby circuit also was shorted as well.
After ruling out every other component on the board I pulled the CPU and determined it was the problem. I had also found a shorted diode on the power supply when I first opened the TV so I suspect that was the cause.
So now, after at least 3 days (might have been more because when I get into a project I lose all track of time) I am unable to find a source for a replacement CPU. I'm hoping someone here might know of one.
The CPU is a Zoran ZR39790HGCG
I was getting no PS_ON from the main and quickly determined that the 3.3v standby was shorted to ground. The voltage regulator for the 3.3v STBY on the analog board was getting hot so that was where I started. The regulator tested ok off the board so I removed a jumper to disconnect it from the digital main. Then I got 3.3v and it no longer got hot so I knew the problem was with the digital main board.
At this point I then located all of the components which the service manual showed were on the 3.3v stby circuit. I removed every component and all tested OK. I suspected the CPU at this point but wanted to be absolutely certain before I removed it. I then discovered that there were more components on that circuit than the service manual showed schematics for. With a lot of help from Photoshop, I traced out the 3.3v stby circuit. This was not an easy task because it's a layered board. So really I only traced out the surface paths.
In the process I determined that the 1.1v stby circuit also was shorted as well.
After ruling out every other component on the board I pulled the CPU and determined it was the problem. I had also found a shorted diode on the power supply when I first opened the TV so I suspect that was the cause.
So now, after at least 3 days (might have been more because when I get into a project I lose all track of time) I am unable to find a source for a replacement CPU. I'm hoping someone here might know of one.
The CPU is a Zoran ZR39790HGCG
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