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[Amps] Modification of AL80A T/R Switch

Subject: [Amps] Modification of AL80A T/R Switch
From: Lee Buller <>
Date: Tue, 25 Mar 2008 08:10:30 -0700 (PDT)
List-post: <">>

I have a venerable AL80A which I do like very much.  Clean and does very good 

I hate the relay clunk from the T/R relay.

I am now putting in a GH-3 Gigavac relay for the output.  Got a nice deal on 
one through Ebay.  Now then, for the imput I am using a smaller relay from 
OMRON which has 3 amp contacts.  Doing the math, the 3 amp contacts are heavy 
enough to handle the 100 watts input with an SWR from 1:1 to 2:1.

The question I have for this august group of amp the bias control 
part.  The relay I purchased is a 4PDT switch with a very quick make and break 
time.  My question is (and this is where my experience gets a little thin) what 
is the ramifications of used the other side of this relay to control the bias?  
The whole B- of the amp goes through this relay...3KV and around 400 or so MA. 
(I do not load this thing up past 400 ma as per the Eimac tube specs)  Looking 
at the schematic it says there is only 25VDC unkeyed and 7 VDC keyed.  But, The 
whole B- is going through this switch as a return path to the isolated filament 
transfer for the 3-500Z.  

Now that I have you all laughing at me....could someone clarify this?

Lee - K0WA
"I hate the CLUNK"

In our day and age it seems that Common Sense is in short supply.  If you don't 
have any Common Sense - get some Common Sense and use it.  If you can't find 
any Common Sense, ask for help from somebody who has some Common Sense.  Is 
Common Sense divine?
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