[Amps] brass or BNP hardware

[Roger (sub1)]

On 11/23/2010 12:22 PM, DJ7WW wrote:
> I got both data sheets.
> My saying is that specifications are far exceeded when 3x 3CX800A7 tubes are
> run at 4KW out, not how far they can be pushed before the big bang happens.
>
> The problem is the anode current and voltage limitation, not the dissipation
> with 3CX800s and a large blower.
> Dissipation is smallest when anode current hits its maximum.
>
> The preliminary data sheet specs for absolutely maximum ratings in AB2 are
> 2500V 0.6A and the later specs are 2250V 0,6A.
>
> Running 6KW out with 3 of them exceeds all specs even more.
I believe the amp referred to runs 3 3CPX800A7s which have max ratings 
of 4500V at *8* amps. So basically plate dissipation is the only worry.  
6 KW with 3 of them on SSB is certainly within the realm of possibility 
depending on the power supply and the tank circuit.

Also as to the "typical" operation in the original specs they listed 
single tone out as 1370 watts or 4110 for three.
They also list 0.8A as a typical plate current even though on the other 
side of the page max is listed as 0.6A, so apparently there is a lot of 
leeway in plate current and cathode emission is not limited to 600 mills.

 >And to repeat it, 4-400 specs can also be overrided easily with higher 
anode
The old glass tubes could be over driven due to the large mass of the 
anode, high cathode emission capability, and thermal inertia.
> voltages and more drive.
>
> I did 1200W out with a single 4-125 in the past when our regulations limited
> us to 150W maximum dissipation for the tube(s) in the final according to the
> data sheet.
and I've seen over a KW out from 6AG7s<:-))  Of course there was a bunch 
of them handing upside down in a bucket of water.  I don't know how long 
they would have lasted running SSB like that.<:-))


73

Roger (K8RI)