What is the safest method to plot characteristic curves without ruining the tubes

[avincenty]

I am new to tubes and I have built a rig to test tubes and circuit configurations. I wish to understand the methods of doing manual curve plotting past the Plate dissipation value. I wish to do this for non published operating values, specifically for AB1 push pull applications which from what I have readn and understand, will allow temporary surges above Pd.

I have tried with a few pentodes, but I end up seeing sparkles and having oscillations on the tubes. Is it actually possible without some type of on off sequencing to average the dissipation?

Alfredo

 

[ashok]

Maybe run a few low frequency pulses and use a peak hold meter ?