Noise problem

[catalin gramada]

... 20220417_231439.mp4

yellow-plate
blue-cathode

I.will try to find a similar tube to test it.

[catalin gramada]

Swapped the tube with another 12bh7 and bouncing the same please.

[Helmholtz]

[URL=filedata/fetch?id=958456&d=1650226778]

yellow-plate
blue-cathode

Thanks, voltage variations are clearly related.
Can you determine, how much the cathode voltage changes per 1V plate voltage change?

[catalin gramada]

Well, it didn't bouncing so much now, the plate more like +/- 0.2-0.3 v max with an average of 0.02-0.05v. The cathode follow less than half. This is an empirical estimation of what I saw on the screen. I.m not able to use the scope to do precise value determination.

[Enzo]

I didn't mean to confuse. You are chasing noise, which I assumed was the HF stuff. I was trying to suggest the bouncing is normal and to be ignored.