[R-390] 6080 in place of 6802 - RMS ???

[David Wise]

> From: Bob Camp [mailto:bob@cq.nu]
> 
> High power tubes do sometimes use direct heated filaments 
> with DC on them.
> It's not to common but it is done. In that case standard 
> operating practice
> is/was to reverse the filament leads once a month to even out 
> the "wear" on
> the filament. One interesting place it's documented is in a 

I suspect that the wear is electromigration.
Anything with DC going through it moves, atom
by atom.  Wherever the current density is
the highest, this effect is the most pronounced,
resulting in a progressive necking down of the
wire.  This is why lamps run much longer on
AC than on DC.

Regards,
Dave Wise