4600
I will look for a neck board.
I did not read the whole thread you listed so i will ask this. Did you measure in Ohms(power off) pin 9 and 10 after you had your voltage. Ohms should be around 4 ohms. If no ohms or even way higher then your tube is bad.
9 and 10 is your heater inputs so if ohms is too high, then less bright on tube and flyback might be bad, because it is working to hard.