[Amps] Modification of AL80A T/R Switch

[Lee Buller]

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

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 builders...is 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?