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Re: [Amps] Alpha 77 start up

To: "Jan Ditzian" <>, <>
Subject: Re: [Amps] Alpha 77 start up
From: "Paul Christensen" <>
Date: Mon, 28 Feb 2011 09:49:07 -0500
List-post: <">>
>   6. *On the top of K5, no two pins are connected.*  AHA!  It seems to
>      me that the pins on top are the contact pins, and that two of
>      these should be connected at all times.


I think your reasoning is good.  I'm not sure how the amp ever worked with 
the configuration you've described.  K5 has all terminals populated.  Two on 
the bottom for the coil and three on the top for the SPDT operation.  Coil 
resistance is about 300 ohms.

There should be DC continuity between RF IN and RF OUT when the amp is 
powered off and the RF AUX ANT switch is in the THRU position.  When the 
slide switch is placed in the AUX position, you should measure DC continuity 
between RX AUX ANT and RF OUT.

I'm not sure the vacuum relay is actually bad  -- or that it's simply not 
wired correctly.   Check for continuity on the relay terminals and if 
possible, apply 26V from an external bench supply to activate the relay for 
DC resistance measurements.  If it's still bad, I would go for a new 26.5V 
Gigavac GH-1 from MaxGain.

> "The tuned/untuned switch does not appear to work.

I think it's correct based on your description.  If you look at the 
schematic, the tuned network is a switched shunt leg to ground.  The 
tuned/untuned INPUT switch only has two terminals connected.

Paul, W9AC 

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