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Re: [Amps] Replacing padder caps on an Alpha 77DX / SX

To: <>, "Jim" <>
Subject: Re: [Amps] Replacing padder caps on an Alpha 77DX / SX
From: "Carl" <>
Date: Mon, 25 Mar 2019 15:09:14 -0400
List-post: <>
I hate to break the news to you but I have a few decades more experience building, using, and servicing amps than you can claim so back off on the snotty comments. That includes a couple of commercial ISM products.

Getting back to the 2 holer AL-1500, it will handle ~ 3dB over 1500W and survive if only done for short periods such as in a pileup and a bit of extra air. A stiff 240-250V line is a given as well as using a better PS board if the HV exceeds the cap ratings. In normal use the tubes are loafing.

The tuning networks are up to the users but are easily tweaked if wanted as is an external transformer.


----- Original Message ----- From: "Jim" <>
To: <>
Sent: Sunday, March 24, 2019 8:40 PM
Subject: Re: [Amps] Replacing padder caps on an Alpha 77DX / SX

If you think that adding a second tube double the plate load impedance....

then you don't understand how linear amplifiers work.

Now if you double the plate current, (1.8 amps, which a stock AL1500 wont do) then the plate load is half.

But the best you could hope for is 1.1 amps or perhaps a little bit higher on CW or SSB... Then it would certaly increase.

Last time I checked, plate load is a function of plate voltage and plate current. Nothing more... Nothing less.

Good luck getting 3600 to 4000 watts output from an AL1500.

Jim W7RY

On 3/23/2019 1:58 PM, Jim Thomson wrote:
From: "Carl" <>
To: "Paul Christensen" <>, <>
Subject: Re: [Amps] Amps Digest, Vol 195, Issue 10--Replacing padder
caps on an Alpha 77DX/SX

<And also 2 holer AL-1500's which was as simple as using the AL-82 tube
<chassis and a filament transformer. W8JI pioneered that swap for his own use.

<Never had a report of any failures.


## Very slick ! Is the oem PI net retained ? The resulting plate load Z with a pair of 8877s would only be one half of a single tube. The 2 holer would require
double the  tune and load C..and  one half the UH  on each band.

##  Was an out board  B+  supply used ?

Jim   VE7RF

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