Weird or What: 45 rewire

Somewhere along the line I bought about a dozen 45 tubes with bare nickel anodes. If memory serves me well this is the reason I went after them at the time. While admiring the tubes I noticed the plates were further apar than normal 45s and then it dawned on me there were extra posts inside the anode as well... for a second grid. At first I thought it was a 46 that was just triode strapped, but the filament deviates a lot. I think these are tubes that were labeled as 45s just to sell old stock? The 45 is etched into the glass, so it's not some hack job by one of the retailers.


Here are the measurements:

What a 45 should look like, take or give

2.5V/1.5A filament
1700 ohms
2050 µA/V

What I measure on 3 tubes (took the one that was in the middle for this example).

2.5V at ±0.125A filament    WTF ?!?!??!?!!?
2080 ohms
2300 µA/V

The gm is higher, as is the mu, that would be one thing on it's own, but the bias is 23V lower. These things would have never worked in a 45 setup.



The tube is very linear despite being a Franken45, easy filament supply. Seeing as I have a dozen or so of these tubes, I will use them somewhere down the line.