just as we were beginning to enjoy this amp, one tube bacame gassy....
so what to do?
well, i replaced to octal socket to septar 7 pin socket once more,
this amp has gone full circle, from a failed 829b set to a 5898....
http://www.r-type.org/exhib/aaa0001.htmthe difference between the 829 and 5894 tubes are:
1. 5894 has a single cathode, this makes the transconductance identical for both plates
since there is only one source of cathode currents unlike in the 829b which had two cathodes tied together..
2. the 829b has 30 watts of plate dissipation per plate compared to just 20 watts for the 5894
3. the plate pins are thicker on the 5894 than with the 829b....
some are of the opinion that these two tubes are interchangeable, this maybe
but i caution you that plate caps once used in the 5894 will not be usable for the 829b anymore
as it would have become loose...
after rewiring...
power draw is around 110 watts, very similar to the 7403....
operating point is 300volts plate at 80mA cathode, for about 12 watts per plate...
this is way below the 40 watt limit for this tube...
in the dark....