12LP4 with FANTASTIC emission...but weak cutoff..OK?

[Eric H]

Originally Posted by Polaraligned

Do we not need to set cutoff in range before proceeding to emissions?
The emissions test results vary with the cutoff setting.

That's how it works with the B&K testers, you can make a weak tube check good by cranking up the cutoff voltage.
I have no experience with the CR70 so I can't say on that.

I have a tube I rejuvenated that has great emissions but the cutoff won't respond all, still it makes a bright raster.

[Phil Nelson]

I have had similar experiences with my CR-70. The cutoff may look bad, but if you turn it up the emission looks good, and when you put the CRT in a TV, it looks fine. I don't know exactly what the CR-70's cutoff test is checking, but the results don't seem very meaningful. The best tester by far is the TV.

Phil Nelson

[Kevin Kuehn]

Just my armchair theory - I think the key is that the cutoff setting has some range of control over the tubes emission. With little control there would be poor contrast in the resulting picture. Most sets have a brightness and contrast control to get the tube operating at a usable background level.