An AL80A has one 3-500Z and the transformer certainly can't handle a
pair of 3cx400 or 800s. Also the bandswitch is a weak spot even for the
stock setup, as is the tank coil. So unless all you are re-using is the
chassis, it would be simplest to hunt around for another 3-500z. Maybe
someone will trade one for one of the other tubes!
73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco
On 29/10/2024 19:53, Mike McCarthy, W1NR via Amps wrote:
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.
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