[Moon-net] 4CX250B questions

[tom]

Hi,

I thought I have been using a pair of 4cx250Bs in my amp (the tubes were not labeled). I had been able to push the output to 800W in CW service for a number of years by increasing the drive to 7-8W from 4W.  I just replaced the tubes with new Eimac 4cx250Bs and cannot push the output past 500W regardless of drive level. Should I be able to?  Running 2000V on the plates in push-pull. The only difference between the new tubes and the old ones is that the ceramic on the old tubes is purple instead of white.  Perhaps they're not 250Bs?

One other question....any special break-in procedure on the new 250Bs other than running only filaments for 24 hrs?


Tom