That doesn't seem right at all. Even if the amplifier is cathode driven, it's way too much drive and the wrong way to use this tube. The screen does not like being treated like a triode. Even swamping the control grid with a 50 ohm dummy load wouldn't require this much drive to reach the needed grid RF voltage. This will require some pictures of the underside, to determine what is going on.
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tennessee walker
- Thread starter 2112
- Start date
Yes thank you. I was going to say that the 4CX250B only needs 2 watts for full output when grid driven and the screen cannot handle ANY power. I have used them in FM broadcast driver stages and they blow easily with any screen dissipation. As you say even if cathode driven that power input is beyond ridiculous. At 1500 watts I am surprised he can keep a pair of them in the sockets.
I believe one of my locals is driving a 250b johnboy with a stryker. I think hes feeding it around 70 watts pep.
As Shockwave said, even with a 50ohm resistor to ground. No more than 80-100W pep is needed to drive amp. Usually the bias is fairly low on those as well, so would need even less. I’ve used 100 ohm going to grid and it didn’t need but 15W pep to get full power out of a pair. At $200 a piece plus shipping from RF parts, it’s going to get expensive quick.
