[Amps] 833C tubes - low filament current

[Mike Waters]

The filament of either an 833A or 833C triode is rated at 10 volts at 10
amps per tube (in a number of tube data sheets I have AND the tube
manufacturer's web site).

However, all six graphite-plate Chinese 833Cs I have here only draw about
half the rated filament current at 10.0 volts measured with two different
Amprobes. The entire filament is lit, and the voltage was accurately
measured with two different DVMs directly at the tube pins.

Has anyone else experienced the same thing?

These tubes are pulls with little use (probably) from a decommissioned
Gates AM BCB transmitter. Five of them look brand new. I have two of them
in parallel in a swamped-grid-driven AB2 linear amp I built, that I'm using
on 160m.

73, Mike
www.w0btu.com