Mod to prevent cathode follower arcing on startup

[catalin gramada]

Thanks, Catalin. So, this arcing really is a warmup issue. Once the CF is warmed up, and conducting, when the standby is turned off, even if the HV is higher than normal by 20-30v, it might not be enough to cause an arc. Id love to build a test circuit, and put increasing HT on the grid, and see what happens when the standby is turned off, and at what point (if any) an arc would occur, with a warmed up, conducting tube.

Someone consider a hundred volts as a safe limit. For this reason a diode or neon bulb will work. As time the voltage drop below 90v it will be blocked so in fact is out of circuit.

[Helmholtz]

the cathode follower has a tendency to arc.

As you speak of arcing: Has anybody really seen an arc?
I think arcing at a "lowish" voltage of 450V or so would mean poor vacuum. Which tube brands are concerned?

I re-read Nick's thread on DCCF failures and found no indication of arcing between any electrodes. (Hope Nick will chime in).

[Greg_L]

I have no expertise to add, but I will say that there about a million JTM45s out there that aren't having any problems with the stock circuit. You don't need to fix a problem that doesn't really exist.