Sell the 3cx400s for close to $250-300 each - post on eHam and they will
evaporate quickly;
Buy new 3-500zs for about the same on eBay.
OR
Sell the 3CX800s for $500-1000 the same way and
Buy a good Alpha 78 (Actually about 4 of them) and keep the 8874s for your
great great great grandkids to use as spares.
Don't beat yourself to death redesigning 60-year old radio hardware to make it
look like 40-year old radio hardware. If the power supply burned itself up,
there is a reason.
(If you still want a project, replace the Alpha plate chokes with ones
non-resonant on 24MHz)
😊
David W6DR
-----Original Message-----
From: Amps <amps-bounces@contesting.com> On Behalf Of
amps-request@contesting.com
Sent: Tuesday, October 29, 2024 2:56 PM
To: amps@contesting.com
Subject: Amps Digest, Vol 262, Issue 17
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Today's Topics:
1. 3-500z substitutes (Paul Decker)
2. Re: 3-500z substitutes (Mike McCarthy, W1NR)
3. Re: 3-500z substitutes (Victor Rosenthal 4X6GP)
4. Re: 3-500z substitutes (Victor Rosenthal)
5. Re: 3-500z substitutes (Aleksandar Petkovic)
----------------------------------------------------------------------
Message: 1
Date: Tue, 29 Oct 2024 12:56:46 -0400 (EDT)
From: Paul Decker <kg7hf@comcast.net>
To: amps@contesting.com, amps-request@contesting.com
Subject: [Amps] 3-500z substitutes
Message-ID: <921267819.1276116.1730221006085@connect.xfinity.com>
Content-Type: text/plain; charset=UTF-8
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.
------------------------------
Message: 2
Date: Tue, 29 Oct 2024 13:53:39 -0400
From: "Mike McCarthy, W1NR" <lists@w1nr.net>
To: amps@contesting.com
Subject: Re: [Amps] 3-500z substitutes
Message-ID: <cfaae6a7-ba2f-4a1b-b600-e9611b05b14e@w1nr.net>
Content-Type: text/plain; charset=UTF-8; format=flowed
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 -
------------------------------
Message: 3
Date: Tue, 29 Oct 2024 20:43:03 +0200
From: Victor Rosenthal 4X6GP <k2vco.vic@gmail.com>
To: amps@contesting.com
Subject: Re: [Amps] 3-500z substitutes
Message-ID: <fe7494c6-fd0f-40d1-8802-c69d815bd301@gmail.com>
Content-Type: text/plain; charset="UTF-8"
------------------------------
Message: 4
Date: Tue, 29 Oct 2024 20:43:37 +0200
From: Victor Rosenthal <k2vco.vic@gmail.com>
To: amps@contesting.com
Subject: Re: [Amps] 3-500z substitutes
Message-ID: <25f70274-7990-400e-b7f9-85272db0e4c0@gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
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.
>
>
------------------------------
Message: 5
Date: Wed, 30 Oct 2024 05:56:00 +0800
From: Aleksandar Petkovic <vk6apk@bigpond.com>
To: amps@contesting.com
Subject: Re: [Amps] 3-500z substitutes
Message-ID: <b3766870-1f51-4579-b149-8e732155915c@bigpond.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Easy. Sell some of your tubes and buy a new 3-500Z.
73, Alek VK6APK
PS: what would you want for a pair of 3CX800A7s?
On 30/10/2024 12:56 am, 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.
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
------------------------------
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