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

To: "Mike McCarthy,W1NR" <>, "Roger (K8RI)" <>, "" <>
Subject: Re: [Amps] Why 2 3CX800s instead of one 8877?
From: Colin Lamb <>
Reply-to: Colin Lamb <>
Date: Tue, 23 Apr 2019 17:19:37 -0700 (GMT-07:00)
List-post: <>
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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