> > At 175 mA, grid dissipation is 18 watts.
> >
> > These figures are from Eimac's tube calculation software.
>
> Works for me, Tom..I do provide a pot on the front panels to adjust
> the threshold to whatever necessary.
>
> I don't run my 8877's at 3300 volts; I run them @ 3999 volts key down.
> Less drive required (65ma) for 2250 watts out. The YU-158 is even easier
> to drive. (10ma less Ig for same output) I have noticed a phenomina with
> these tubes. (8877)/YU-158) They seem to "shift into overdrive" at
> 3700-3800v. Much less Ip and Ig.
Prices of commercial amps skyrocket when HV gets above 3500
volts or so. That makes it necessary to live will around 11 watts of
grid dissipation, but that is still safe with a grid short term average
rating of 20 watts. Eimac puts some headroom on the grid
dissipation figure anyway.
8877's became a constant source of problems when manufacturing
was moved to Salt Lake. Now that the tubes are being made in
San Carlos, the problems have all but vanished. The 8877 is a
reliable tube again.
73, Tom W8JI
w8ji@contesting.com
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|