On Monday, 29 April 2019 04:03:25 UTC+1, wrote:
NT:

"Well I've done it when all else failed, and it would not result in excessive x-ray emission. I kept one such set for 10 years or so, it kept going just fine. Why do you dislike it? "

Well you got lucky. High voltage components are particularly prone to failure even at their rated voltage and you may not have had problems, but I bet out of 10 times at least 7 would be a problem.

There is a small failure rate at the original voltage. TV parts are generally run well below parts mfrs' rated voltage to improve reliability, eg 25kV on a 40kV part, 15kV on a 25kV part. Failure rate climbs as you apply more, but it only takes a small boost, 5-10%, and the increase in failures is not great for that much. But yes it's there. However the key phrase is when all else fails. 90% beats 0% by a long way.

Cleaning the EHT stuff always helps, dirt degrades insulation capability..

Another thing is what did you do about deflection sensitivity ?

Raise B+ the same amount. In TVs the easiest way is just to raise B+ across the board.

How do you know it did not result in excessive Xray emission ? Piece of plywood and some photographic film in a dark room ?

The OP has a 500v tube. Otherwise look up the datasheet for the CRT, they're often run below rated v.

You can also use a counter. It can't measure all the tube's output, but it can measure background, and relative original & boosted outputs. Then you know what %age the increase is and can see if that's within requirements.


NT