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[Amps] 3-500z substitutes

To: amps@contesting.com, amps-request@contesting.com
Subject: [Amps] 3-500z substitutes
From: Paul Decker via Amps <amps@contesting.com>
Reply-to: Paul Decker <kg7hf@comcast.net>
Date: Tue, 29 Oct 2024 12:56:46 -0400 (EDT)
List-post: <mailto:amps@contesting.com>
Hey gang.
I'm the proud owner of an AL-80A that's an absolute basket case. Tube is gone, 
HV section looks like it needs a rebuild. 

My "in stock tubes are: Qty 6 - GI-46B, Qty 6 - 3cx800A7 and U7, Qty 6 - 
3cx400A7 and U7, Qty 2 -TH308, Qty 2 -TH328, Qty 2 - 8791, Qty 4 - 7213, Qty 2 
- 7650, Qty 2 - 4cx1500B, (4cx350/250/150, 2c39, some other power tubes I don't 
really know) and sockets for all except the GI-46B and 4cx1500B.  

The goal is "fix'er up" with buying as little as possible. I'm leaning towards 
the GI-46B an the other triodes since there is no need for any extra screen 
bias voltages or control. The pair of 3cx400U7's (or 800's) would fit in real 
nice too, except it then requires some kind of forced air cooling mechanism. 

It looks like it's using a voltage doubler for a no load voltage of 3000V and 
loaded voltage of 2700V. I could pull a few windings off the transformer to 
lower it down a bit for the 3cx400/800 tubes, or just run at 2700. 

What do you all think would be the best fixer up route?   

Paul.

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