> > At 2250 watts output, an 8877 draws less than 65 ma grid current.
> > 75 ma limiting is plenty of headroom. A cap sits in the base circuit
> > of the TIP120 to prevent nuisence trips.
>
> 75 mA is not plenty of headroom Phil.
>
> At 3300 volts anode, a typical 8877 requires 125 mA of grid current
> to produce 2500 watts output, At 125 mA of grid current, grid
> dissipation is 11 watts.
>
> 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.
(((73)))
Phil, K5PC
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