On Sat, 23 Jan 1999 13:28:11 -0800 dan hearn <dhearn@ix.netcom.com>
writes:
>
>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
It has been a few years since I have worked on one of those amps but my
notes indicate 70 ma grid current for 2300W out with 100W drive.
The AL-1500 manual says 100ma absolute maximum and my experience has
again been around 70ma for close to 2500W.
The 1500W level requires 60-70W drive and grid current around 50ma in
both amps assuming a full output 8877.
73 Carl KM1H
>
>
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>
>
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