Oh no! Not another TV Damper tube. I know that I show a lot of these but they are my favourite rectifier devices. So they deserve being covered. Most of the odd heater variants of the 6AX4 have been shown already, the only one missing is the 12AX4.
RCA data sheet for all details. Since such heater variants are not very popular, these tubes can be picked up at cheap prices. Maybe the 12AX4 would be the right choice for a project which uses 12.6V heater tubes throughout.
Here we have a Sylvania 12AX4GTB with coin base.
The 'GT' in the suffix stands for glass tube and B indicates a later version with improved specs.
A few detail shots.
On the base unused pins are left out to increase creepage distances for high voltages.
Another Sylvania also with coin base.
Next we have a Westinghouse with full base:
And lastly 3 slightly different looking General Electric 12AX4GTB:
Although internal construction appears to be identical in all 3, they differ in color and placement of the printing.
The next one:
And the third:
Since I already dissected a lot of TV Damper tubes I did not intend to break one of these. But since I accidentally dropped one while taking photos, we might as well have a look at it's internal construction.