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[email protected] jurb6006@gmail.com is offline
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Default Marantz Model 19 Scope

"I've been dealing with a slightly similar problem myself... I bought a CTS service monitor whose scope is working-but-dim. Fortunately it has a 3RP CRT (like the Cushman and Macintosh systems do) and I have a local source for a used tube (and there are online sources as well). "

Have you tried boosting the filament voltage ? For one it is the best way to extend the life of a CRT, rather than rejuvinating. I wouldn't recommend that for a CRT unless it was in a TV, the color CRTs pull quite a bit of current and guess where it all comes from - the cathodes.

But scope cathodes don't get loaded heavily. they can be just as bright as a tube pulling 20 times more current easily because they are not generating a raster.

If it turns out to be weak emission in this tube I am not exactly sure how to boost the filament voltage. It seems to run off a resistive divider, but for a small tube which is a RAY type tube not a raster type it is sufficient. But then doing anything in that circuit might do something to the G1 bias or whatever.

Thing is also figuring out how to actually test the thing if/when all the other possibilities are eliminated...