You can check the voltage through the X and Y sustain boards to see which is damaged.
Voltage travels the following direction on these TVs:
Power Supply: http://www.discount-merchant.com/We-provide-factory-original-parts-worldwide-p/1 075235-zenith.htm
Then through Y-SUSTAIN: http://www.discount-merchant.com/Y-SUSTAIN-PN-6870QYC004A-6870QYC004B-6870QYC004 C-p/vizio-sku9501.htm
Bythe way.. This is the MOST POPULAR failing part on these TV's... Abovelink has it for $154.99 and the quality and shipping time isoutstanding. Be careful buying from a used dealer or someone not as bigas Discount-Merchant is on parts. You may get a part that lasts 1/2 thetime. These boards are like DLP TV lamps, they have a limited lifetimeand if you buy from the wrong place, you will have to replace it moreoften and it can damage other components when it pops!
Next Power travels through X-SUSTAIN: http://www.discount-merchant.com/Vizio-SKU9502-p/vizio-sku9502-psp.htm
Again.. only $154.99 and this is the 2nd most common failing part on these TV's..
To test which board is bad you need a multimeter... then test for the following:
1.disconnect the power board from the y-sustain board.. Check input intopower board (is voltage coming in from the wall?) Next, test forvoltage going out of the power supply.
2. Next test voltagegoing to the Y-SUSTAIN BOARD by having everything connected except thelink between YSUS and XSUS. Check for voltage going into YSUS (if powersupply is putting out, then ysus shoudl be receiving).. Next, test forhigh voltage comming out of the YSUS... keep in mind, xsus isdisconnected.
If you get power comming out of the YSUS, this means your YSUS is GOOD and your XSUS is BAD....
If you get no power comming out of the YSUS this means that the YSUS isBAD.. in this case you need to replace your YSUS, however, you XSUS canalso fail when your YSUS blows out.
In order to test yourXSUS, you can use a multimeter to test breaking in the transistormodule that has the big Black or Silver heatsink on it. You can test itby using a multimeter and applying it to the bottom pins of the board.
Again,Discount-Merchant.com seems to have many of these boards in stock andthey are my lifesaver! The price is VERY LOW compared to anyone else,and the quality is outstanding. 1 year buying these boards from themwithout a single returned customer.
I bought one off of somejimmy guy on ebay and it blew in 1 month. I though i was saving myselfmoney but the customer was back and very upset. Be careful!