[TinCanAlley]

Originally Posted by old_tv_nut

The Zener is not connected to two grounds, because the spark gap is an open circuit until the voltage gets very high and causes a spark. It is there probably to protect the Zener from being killed in case of a CRT arc.

I don't know if the Zener is supposed to be always regulating at 7.5 volts, or just limiting the voltage to 7.5 volts if it tries to go higher. You can find out by measuring the voltage from the top of the Zener to ground (or scoping the top) to see if it is 7.5 volts, or if it is less.

Hang in here with me. Now isn't the 500ohm 7w resistor connected to the ground of the tripler? If so, then isn't the zener connect to that (ground) AND to the chassis point (ground).

I've attached a pic of the underside. I've circled the connections in question. In the left circle is the black wire which connects to the 500ohm resistor on the tripler ground, the white/green wire to the brightness limiter pot's T1, one leg of the zener and one leg of the spark gap. The right circle is a ground point (soldered to the chassis' top side) that contains the other leg of the zener and spark gap. I'm hoping you can understand why I see nothing but grounds and no voltage for the zener.