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[Amps] Metering Problem Heathkit HA-10 Amp

To: Glowbugs <>, Heathkit List <HEATH@LISTSERV.TEMPE.GOV>,
Subject: [Amps] Metering Problem Heathkit HA-10 Amp
From: Allen Jones <>
Date: Thu, 13 Mar 2008 11:25:42 -0700 (PDT)
List-post: <">>
For the last two weeks I have been wrestling a
Heathkit Warrior around on the bench installing a new
plate transformer and modifying the grid circuit.

The amp originally bypassed the grids to ground with
capacitors and metered grid current directly.  I have
bonded the grids to ground using braid and metering
grid and plate current at the center tap of the
filament transformer.  A 20K 25W resistor and a 5.1V
zener are in series with the filament CT to ground. 
The resistor is shorted out with a relay when the amp
is keyed.  The negative end of the supply is held 25
Ohms above ground so as to meter plate current there. 
The plus side of the multimeter is connected to anode
of the zener and the negative is switched between
ground to read grid current or B- to measure plate
current.  Pretty much a standard Handbook arrangement.
I am doing my testing WITHOUT the 811A's.

When I power up, the meter is pinning (not hard)
negative and I see a small upward scale deflection
when I switch to the plate position.  I pulled the
solid state 866 replacements (the fil xfmr for the
866's has been removed) and see no current flow so I
assume that somehow or another I am reading bleeder
current. I verified this with the temporary addition
of 100K in series with the existing 60K bleeder.  The
deflection of the meter in both positions is less. 
The grid no longer pins but still deflects negative.

Anyone have any ideas?  Could a leaky component be at


Allen, W9DZ

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