[Amps] Why 2 3CX800s instead of one 8877?

[Alek Petkovic]

Ha. That's what ya call "thinkin' outside the anode."

Cheers, Alek.
VK6APK

On 26/04/2019 5:40 AM, Carl wrote:
> Since a pair of 3CX800's wont even come close to running hard in a 2 
> or 3 hole 76A series amp then a little careful surgery will do the trick.
> Remove enough of the anode cooler from both tubes so that they will 
> fit with about 1/4" spacing.
>
> Dont laugh, it is just a part of hams doing what works when needed.
> I modified several 8874's decades ago to replace the 8873 in Heath 
> SB-230 amps. At that time they were cheap as full power medical and 
> other pulls.
> My own SB-230 modified for 6M and used for portable and roving has 
> been fine since 1985.
>
> Carl
>
>
>
> ----- Original Message ----- From: "Colin Lamb" <k7fm at teleport.com>
> To: "Mike McCarthy,W1NR" <lists at w1nr.net>; "Roger (K8RI)" 
> <k8ri at rogerhalstead.com>; <amps at contesting.com>
> Sent: Tuesday, April 23, 2019 8:19 PM
> Subject: Re: [Amps] Why 2 3CX800s instead of one 8877?
>
>
>> I am somewhat mystified by the messages.  The Alpha 76A has 2 or 3 
>> tubes 3CX400.  But there is a difference.  The 3 tube version you can 
>> plug one socket and then use 2 3CX800A7 tubes.  They fit fine.  I 
>> changed one and mounted the transformer inside the unit.  It works fine.
>>
>> There is a problem with the two tube version.  If you change to tubes 
>> to 2 3CX800 tubes - the sockets are too close together so they do not 
>> fit. That would require more work because the holes and all the 
>> chimenys are too close together.  I have a 2 hole amp and used the 
>> 3CX400 tubes.  I run that amp at 1200 watts and it has run flawlessly 
>> for years.
>>
>> I did a couple of other things to my amp.  I installed a vertical 
>> array inside between two meters for grid response.  Because these 
>> LEDs are much quicker that the meter it is much faster and that lets 
>> me monitor forward output with the meter.  Then, I converted the 
>> output meter to read peak reading with a meter used for the Bird 
>> Wattmeter.  I have about 6 amplifiers and with those two changes this 
>> amp is the one I use day after day.
>>
>> 73,  Colin  K7FM
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>
>
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