Steve,

If you move a lot of air around the 811 tubes, you can hammer the daylights 
out of them.  I bought a high speed fan one day and laid it on top of the 
area of the tubes and the entire amplifier casing of the Warrior was cool to 
the touch even after operating for hours.  Without that fan and with just 
the one Heath Kit built in fan of the Warrior, the metal knobs even got so 
hot you could hardly touch them.  I drilled some holes internally to allow 
more air to pass by the tubes but although it helped some, it wasn't good 
enough.  When I bought this high speed fan, which was built into a frame, 
and laid it over the tubes, you could hardly hear yourself talk without 
using headphones, haha.  I know it helped a lot more moving all that air but 
you are right about buying 811 tubes today compared to 20 years ago.  I 
always thought about buying 572B replacements for the 4 811A tubes the 
Warrior ran but I figured I'd over do it and just burn them up as quickly as 
the others.  I got hundreds of ours out of my 811a tubes and I ran them for 
as long as possible before buying new ones.  Shoot, I couldn't even lift 
that Warrior these days but when you are 30 years old with three little kids 
running around, you can do a lot more it seems, haha.

Phil.
K0NX




----- Original Message ----- 
From: "Steve" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, April 27, 2014 6:48 PM
Subject: Re: Re 811H


> The 811H of course runs 811's.  But you can swap them out for 572B's, 
> which
> are more rugged.
>
> The thing you have to be careful with the 811's is plate dissipation.  The
> tubes are rated for 65-watts average plate dissipation.  This is fine in 
> SSB
> operation, but is more damaging to the tubes if you push them on heavier
> duty cycles like CW, RTTY, etc.
>
> A lot of hams have issues with those amps if they spend too much time
> tuning.  You have to let the amp rest for about as long as you apply a
> carrier to bring the average plate dissipation down.
>
> Another bigger issue today is the quality of the 811A tubes.  Some
> manufacturers aren't keeping the quality up.
>
> Steve, K8SP
>
>
> ----- Original Message ----- 
> From: "Phil Scovell" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Sunday, April 27, 2014 8:34 PM
> Subject: Re: Re 811H
>
>
>> Mike,
>>
>> That's about what I thought it would run.  I just was curious because a
>> friend has one but he pushes his much harder than you do and has to buys 
>> a
>> round of tubes more often than needed.  I believe he actually bought 4 of
>> the 572B  tubes and then he didn't push it so hard because he didn't want
>> to
>> keep buying tubes.
>