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

[Carl]

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
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps 


---
This email has been checked for viruses by AVG.
https://www.avg.com