Why not start with a pair of 4-125A's in grounded grid...
They will give you the same output as a pair of 813's and 3KV plate voltage
is within their spec.
Later by simply beefing up the plate supply and filament transformer and
choke you can
upgrade to 4-250A or 4-400A or 3-500Z with out changing sockets. You will
probably be content with
a pair of 4-125A's for some time. Also, don't forget to make a window so
you can enjoy the red glow of you
plates....
4-125's are cheap because very few people use them and you are
more likely to get
new ones than the 813's. Many of the 813's I have gotten at hamfest were
abused and usually low on emission.
Hams used to push them hard since they were cheap in the 50's and 60's
73
Bill wa4lav
At 09:37 PM 10/10/01 -0700, Geo Clute W7LFD wrote:
> >-----Original Message-----
> >From: owner-amps@contesting.com [mailto:owner-amps@contesting.com]On
> >Behalf Of Mike Baker
> >Sent: Wednesday, October 10, 2001 10:37 AM
> >To: AMPS REFLECTOR; Jean-Michel Bombar
> >Subject: Re: [AMPS] Help building mono band amp
><snip>
> For any band up to 20 meters they kick butt and love high voltage.
><snip>
>
>The 813's typical operation is to 30 MHz. I ran a pair on 10 meters
>with 3350VDC on the plates.
>Drove them with a Swan 500cx until the carbon plates many red
>hues...Couldn't burn them out.
>
>1983 "The Radio Amateur's Handbook"
>Freq.: 30 Mc.
>Plate V. 2500
>Plate MA 125
>Screen ma. 20
>fil 10v 5A
>Screen Volts 800
>Cin PF 16.3
>C gp PF .025
>C out PF 14
>
>Typical output AB2 two tubes is 650 W
>
>Regards,
>
>Geo W7LFD
>
>
>
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