Rich writes:
> K-202 looks like it's a grid shutoff.
There is no K-202 on the schematic or parts list of the PA-374, PA-76
or PA-78 amplifiers on the BAMA site. Those are the only amplifiers
produced by Alpha to use the 8874. In all three cases the grids of
the 8874 are connected directly to the chassis.
Which amplifier/schematic are you looking at?
> > However, since W0UN, AAA0RS and W0ID no longer contribute regularly
> > to this forum - schematics for the 76 and 86 amplifiers are on BAMA
> > if you care to check the facts before you make wild (wrong)
> > statements.
>
> I was looking at Alpha's diagram.
Apparently not the diagrams provided to BAMA by Alpha (W0UN and AE0Q).
> > The manual includes an extensive, well written
> > discussion of tube protection, how it works and how to configure
> > it. However, since it does not agree with your pseudo science you
> > don't acknowledge it - as usual.
>
> The Q1 is a TIP-147 and is rated at 5A. Q1 appears to carry grid
> current. Is this true?
If you read the explanation, Q1 and U1 are an "adjustable zener" that
provide bias. Looking at the schematic they are in the cathode circuit.
The only transistor in the grid circuit is Q6 (page 31, lower left
corner) used in the grid current sensing circuit.
If you bother to read the rest of the manual, you will find the G3SEK
board is designed for use with the grids bolted directly to the chassis.
73,
... Joe, W4TV
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