I have a single tube Alpha 77DX. The instruction book says "The 8877 is
extremely rugged and operates with a large safety margin if grid current
is never allowed to exceed 0.2 amperes, nor plate current 1.0 amperes
per tube." It also says" monitor drive power adjustment so that
amplifier grid current remains in the range of 0.1-0.15 ampere for the
77DF/77DX versions" They specifically state that these values apply to
the single tube version.
The grid current meter is labeled 500 ma full scale. A study of the
resistors in the grid current measuring circuit tells me that it may
actually be 250ma full scale. In order to obtain legal limit output , a
grid current of at least 100 ma indication on the meter (assuming 500 ma
f.s.) is needed. Eimac's data sheet for the 8877 shows a lot less grid
current for 1500w output. Can anyone throw some light on this situation?
Thanks, Dan, N5AR
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