[Amps] Separate B-minus connection is not necessary

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Fri, 06 Nov 2009 20:44:41 +0000, Mark  K5AM <k5am at zianet.com> wrote:

> Even grounded-grid triode
>amplifiers can be configured for this independence; a differential op
>amp circuit can be arranged to measure plate current as
>
>                            Ib = Ik - Ig
>
>where Ik is cathode current and Ig is grid current.

REPLY:

Yes, it could be done, but that's a lot of work, and I do not trust delicate op
amps in the presence of high voltage and high RF. I would suggest a simpler and
more reliable approach:

Use an SPST relay to open the B- line in each unused amplifier. For safety's
sake, a pair of 6A10 diodes should be connected in anti-parallel from B- to
chassis ground inside the power supply, and another pair likewise inside the
amplifier. The relay would be activated when switching from standby to operate.

Problem solved.

73, Bill W6WRT