Mitsubishi WS-65809 - works, but screen won't power on.

yes that is correct 12 is normal...make sure all connectors are plugged in and in the correct places . conectors should be marked with letters that match the marking on the circuit board. Then look for heaters , in the glass bottom of the picture tubes(CRTs) there should be a little orange glow visable though the neck of the CRTs just above where the crt boards plugg onto the bottom. if the heaters are not glowing then check your wires to the crt boards again , you probly tugged one of them too hard during disassembly also check for cracked solder in the heater circuit......Oh yeah, you didn't mention -Does the TV get high voltage ??? thats important to having a picture......If you see the heaters glowing when the tv is on then look down into the lenses of the crts . If you see a brite color horizontal line closer to one side in each of them then you know most of the tv is working. If that line is curved then the tv probly detects that the convergence circuit is not working and it is blanking video.
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the error is 21 (see what number it ends the sequence with..) . Error 21 is X_Ray protect and you probly plugged one of the connectors into the diagnosic connector(near the high voltage transformer- normally nothing goes there) . If that is the case then somthing in the H.V. circuit could have been permanently damaged and now the tv has a new problem and wont work even if you put that connector in the right place.