I read a post by Carl, KM1H on August 10, 2009 that read:
There are several ceramic tubes that are notorious for seal leakage. The
4CX300A is a classic.
This post is directed to Carl. The list might also be interested. I would be
interested in a brief explanation of the problem.
I have 7 NOS JAN 4CX300A's an am building a 3 tube passive grid driven amp. The
date codes are 7204, 7432 and 7634 if this makes a difference. Are the JAN
Eimac tubes less problematic?
The amp is in a simibreadboard state with 4CX250B's. Since I now have 3 sockets
for the 4CX300A's, I will switch tubes and raise the Ep to 2500 V. I do not
want to waste my time if I am going to have a problem with this change.
John WA4EPI
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