Hello , my name is Jack
Sorry it took a while to get a reply , just got online myself.Perhaps I can help you with this problem but first I must say that from your description about the picture that blinks , I would have suggested the backlight inverter to start with.
As it turns out the backlight inverter is part of the power board and that could very well account for the pops in the audio circuit as the whole power board would be affected by that blinking backlight.
There are two versions of that power/inverter board for your tv .
On the bar coded sticker there would be a number that would either look like this one 0500-0405-1340 or this one 0500-0412-1360
Do you have the back cover removed at this time ?
Where did you get your main board ?
I have the 0500-0405-1340 and got the main from ebay...Could this problem be the display?
From what you said , I understand that the backlighting is flickering ?
Flashes bright and dark like a strobe effect ?
yes but not real fast but just about once a second as well as the audio
O.k then I would still suspect the power/inverter board .
I would be very surprise if the lcd panel would be the culprit.
In any case you can return that board minus a 25% re-stocking fee ($17) at the link I will give you if the panel proves to be the culprit.
Definitely worth a try .
Not sure about your main board though , perhaps you can return it ?
here is that link for the power board;
Thanks, XXXXX XXXXX been very helpful