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[Amps] 8877 Grid Connection DC or Not

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Subject: [Amps] 8877 Grid Connection DC or Not
From: "Jim Thomson" <>
Date: Wed, 30 Nov 2016 06:20:50 -0800
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Date: Tue, 29 Nov 2016 17:37:27 -0600
From: "Jim W7RY" <>
To: "Radio WC6W" <>, "AMPS" <>
Subject: Re: [Amps] 8877 Grid Connection DC or Not

Marv... Because this will be a single power supply and multiple RF deck (5 
or 6 of them) amplifier system for a contest station.  I dont want to use 
vacuum relays as high voltage switches.

Metering plate current is easy. Simply put the plate current meter (set back 
from the front panel for safety) in series with the HV on the RF deck.

Thats why.

Jim W7RY

##  There was some minor trick to this scheme, that I worked out a few years 
back for
somebody else.  I will try and dig up my old notes.  It used one big B+ supply, 
to  6 x amps.  Each amp used the same type tube.  Each RF deck had its own fil 
xfmr, and
its own plate / grid / HV meter.  

##  If I recall, the B+  was fed to the 6 x amps in the normal fashion.  Ditto 
with the B-. 
Plate current in each RF deck was measured in the normal way, ditto with grid 
IE: B-  coming into back of rf deck fed to NEG of plate current meter. POS of 
current meter bonded to POS of grid current meter.  NEG of grid current meter 
bonded to
chassis.  POS of both grid + plate meter fed towards  CT of fil xfmr.  Usual 
50-100k resistor
in series with the CT, with TR contacts across it.  HV meter in each RF deck 
was wired directly between
incoming B and B-. 

## RVS connected 6A10  diodes wired between B-  and  HV supply.  
Then the B- cant wander more than  
+/-  .7 volt. 

Jim   VE7RF

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