Hi and thanks so much for the help. Pretty sure the LED's are 3V as my meter on diode check only puts out a little over 2V. My meter is able to make the LED's light up dimly, but enough to see if they're working. Unplugged ribbon from main to TCON, no change. I didn't see a rest switch near the RF connector but rather on the adjacent side near composite video and stereo audio inputs (phono or RCA jacks) I pressed this for 15 sec. like you said, no change. Any other ideas? If not I give up and I'm sending the boards back.
Long shot but easy to try: unplug the wifi card and see if the main responds.
There are two versions of the Hisense 58R6E apparently, different main boards but they use the same power supply. Did you measure the voltage on XP702 pins 2N and 2P? If you are getting a large voltage (150 plus) but no visible flash from the back lights as seen from the back side of the display, you still have a problem inside the display. I'm assuming your LED strips are new, but if you bought used ones, there's a high probability they're bad. I've also found bad connectors that plug into the LED strips. I never reassemble any display until the back light runs for at least an hour. If you are not getting that voltage kick on that connector, then the problem is one of the boards.
If you are getting no voltage/flash on the back lights, then check the "STB" line on the power supply connector. On these, the stb is not the standby voltage for the main as you might expect, but the turn on command from the main (counter intuitive but this is the crap we run across). The STB line takes the power supply *out* of standby on these TVs and puts the supply in full run. The actual standby voltage from this power supply is your 12v, which is there because you're getting your red power LED blinking. So check the STB line for voltage to the ground screw near the connector. The STB line should go high (3.3-5V prob) when you push the power button. If you are getting a high on the STB, then check the voltage on the two 450V PFC caps. The voltage on those caps should be close to 400V. If you get a command on the STB but the voltage on the PFC caps stays low (about 160V but doesn't go to 400V), then your PFC controller IC on the bottom of the power supply board is probably bad. It's surface mount but they are available. They do have a drop of glue underneath so it's a good idea to heat it well with hot air before you remove it. If the 400V comes up, it's either the LED supply section of the power supply or the back light command from the main (BRI) isn't there.
If you get no command on the STB line from the remote or power button being pushed, the main is not commanding the power supply to turn on and the main is your problem.
Any boards you are buying are salvage boards, and I know from experience that these are NOT checked despite what the seller tells you. When I'm forced to buy a board, I find about 30% of them bad when I get them.
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