I just replaced a bad quad in my 808s, but now I have a new problem. With the new quad it comes out of standby, but the tubes won't illuminate. I have a good video feed attached to 1, 2, and 4/5. No red LEDs at all. Green LEDs on all three tubes. Adjusting G2 pots does nothing to the green LEDs on the tubes. The controller board has the stdby, main power, and block match LEDs on for ports 1, 2, and 3/4. I swapped out the horizontal board, vertical board, port three board, RGB switcher board, and quad decoder. No change. I checked the 17v point on the SMPS, and it was high - 17.82 - and dialed it back. I've seen reference to a 48v check point, apparently referenced in the service manual, but I only have the owners and installation manuals which I don't believe discuss it. I'm not sure what else to try at this point. Any ideas are warmly appreciated!