Again thanks for the help. Dummy me, test all the new back lights individually and assume that problem is solved. WRONG! Upon plugging the power cord in, no flash. Stuck my trusty meter on XP702 and it initially goes over 200V, then peters out a few volts per second like there's no load whatsoever. It appears to be draining slowly into the power supply. Time to take all the screens apart again and find where the break is.
That's why I don't reassemble until the LEDs run an hour. The more the screen comes apart, the greater the likelihood it won't survive another attempt. Look for one of the plugs not fully seated (I've done that a bunch of times).
General comments on display removal: be very careful with the bonded ribbons - try not to flex them much. If the display is held down with double sided tape, make sure to carefully life the screen out. I use a heat gun (carefully) to heat up each side one by one, and with a small suction cup, pull up while sliding a thin plastic shiv along working until the side is free. I then put some paper towels on the released side so it doesn't rebond when you move to another side. If you try to lift the screen without releasing the tape, the screen WILL crack. Make sure those sheets go back *exactly* as they came out. If you get one upside or backwards or out of order, it will affect the picture as at least one of the sheets is a polarizer. Make sure the four corners of the display itself are safely nestled inside the frame. You can use a combination of feel and magnification if necessary to make sure the screen isn't sitting on the lip even by a micrometer. If the display isn't tucked properly inside the frame, it WILL crack when you snap the outer mask back in place.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.