Quote:
Originally Posted by Kevin Kuehn
That R32 150k you crossed out, what happens if you put that 150k in series with the top leg of the diode? Without that there you're really loading down the signal when the brightness control gets to the extreme ends of it's travel.
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You are not loading down the video when the brightness control is at the end, because the diode only conducts on sync.
However, in the original circuit, the average cathode video voltage is between 0 and 120, but with the diode, the sync peaks are between 0 and 120, and the average is lower (making a brighter picture). You may need to look for a higher voltage for the positive end of the brightness control and put a resistor between the other end of the contol and ground, to get the syncs to be cutoff and normal video to be normal.