[TinCanAlley]

Originally Posted by old_tv_nut

You can rest assured that a damper diode either works or fails - there is no in-between. If it fails, the horizontal sweep doesn't work and you probably will blow a fuse. So, if your set is basically working and your complaint is those jail bars, it's not the damper diode. The zener, on the other hand, could fail open and the effect on operation might not be so obvious.


There are a couple of ways to check the Zener in operation. One is to measure the DC voltage across it and see if it is correct. This presumes that the Zener is conducting during normal circuit operation. But sometimes, a Zener is used in a circuit for over-voltage protection, and then it only conducts if there is a fault; in this case the voltage could be anything less than the specified value.

You can also check with a scope, but this is more complicated unless one end of the zener is grounded, because you have to check both ends and subtract one from the other to see if the voltage difference is constant and equal to the correct value.

This is where my lack of knowledge comes in. Take a look at the pics in this post:

http://videokarma.org/showpost.php?p...22&postcount=3

The schematic of the tripler with the brightness limiter and zener makes my head spin. If I'm reading it correctly, the zener is connected to the ground of the tripler and chassis ground. There's also a spark gap going across those two points. I can't seem to figure out how the zener gets its 7.5V for operation connected to two grounds.