[Amps] 3-500z substitutes

[Mike McCarthy, W1NR]

I would start by comparing the schematic and components of the AL-800 
(factory stock 3cx800A7) just to see what parts are the same and what is 
different. I am assuming they are reasonably close. Biggest difference 
would probably be filament voltage and cathode circuit.

On 10/29/2024 12:56 PM, Paul Decker via Amps wrote:
> 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.


-- 
73 de Mike, W1NR

THAT was the equation. EXISTENCE!... SURVIVAL... must cancel out... 
programming!

- Ruk -