> 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.
You are correct Dan. Several years ago, I spoke with Ray Heaton, ETO's
Service Manager in the early '90s. He confirmed that the 77Dx was
deliberately designed to indicate approximately double the true grid
current, presumably to add an additional 100% safety margin against operator
error.
-Paul, W9AC
----- Original Message -----
From: dan hearn <dhearn@ix.netcom.com>
To: <Amps@www.contesting.com>
Sent: Saturday, January 23, 1999 4:28 PM
Subject: [AMPS] Alpha 77DX grid current
>
>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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>
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