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Re: [Amps] Single Band Amplifiers One Power Supply

To: Jim Thomson <>
Subject: Re: [Amps] Single Band Amplifiers One Power Supply
From: MU 4CX250B <>
Date: Wed, 30 Nov 2016 09:36:54 -0700
List-post: <">>
Running multiple RF decks simultaneously from one HV power supply is a bit
trickier than it might seem at first, especially if you want individual
metering on each RF deck. Grid-driven tetrode amps with grounded cathodes
introduce another complication, especially if mixed with triode amps. Also,
keeping track of the fault currents from flashovers or internal tube arcs
and keeping them from damaging anything can be a challenge. It can be done,
but it's just a bit harder than one might think at first. Here is a photo
of two HV power supplies I built recently, each designed to operate three
RF decks.

Details are in a QEX article I wrote a couple of years ago, and I'm happy
to send a copy to anybody who wants one.
Jim w8zr

Sent from my iPhone

On Nov 30, 2016, at 7:36 AM, Jim Thomson <> wrote:

Date: Sat, 22 Oct 2016 19:07:58 +0000
From: Bill Turner <>
To: Amps group <>
Subject: Re: [Amps] Single Band Amplifiers One Power Supply
On Wed, 19 Oct 2016 18:47:05 -0500, W7RY wrote:

How would you go about metering them?


In modern amps. both the B- and B+ are NOT connected to ground, but
left floating. The grid current meter is connected from B- to ground.
The plate current (actually cathode current) meter is connected in the
B- lead BEFORE the grid current meter    , i.e. on the power supply
side of the B- lead, not the cathode side.

Sounds weird, but it works. Check the schematic of any late model
grounded grid amplifier and that's how they do it.

If you want to use a single switched meter for all the amps. simply
put a low value resistor on the order of one ohm or so where you would
normally put the meter and them simply measure the voltage drop across
it. That way you can switch the meter from one amp to another without
disturbing current flow. Simple Ohm's law will give you the values.

73, Bill W6WRT

## The plate meter will only read plate current, and not cathode current.
The grid meter
will only read grid current.  This assumes u wire the meters like have been
shown in every arrl
book for years.. for a GG triode.  POS of both plate and grid meter bonded
together...then off to the
CT of the fil xfmr.   Neg off plate meter to B-.    Neg of grid meter to

Jim  VE7RF

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