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

[Carl]

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.

Carl


----- Original Message ----- 
From: "Jim" <jimw7ry at gmail.com>
To: <amps at contesting.com>
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.
>
> 73
> Jim W7RY
>
>
> On 3/23/2019 1:58 PM, Jim Thomson wrote:
>> From: "Carl" <km1h at jeremy.qozzy.com>
>> To: "Paul Christensen" <w9ac at arrl.net>, <amps at contesting.com>
>> 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.
>>
>> <Carl
>>
>> ##  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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