The SB200 *could* be used with 811A's IF you could find a way to reduce
the hi-voltage to about 1800 (Max). But this is unlikely due to the SB200's
transformer being one for the hi-v and the fil. voltage and the relay
voltage !!!! the key here is the hi voltage. I have used 811A's in an SB200,
BUT, if you sit down on the key they will last only a few seconds, before
they blush badly and proceed to melt down.!! I have used them for test
purposes but only in an emergency, and then only *very carefully*.
Going the other way, using 572B's in place of 811A's is not too uncommon
since the 572B can handle 2200-2400 volts on the plate, but the 811A's are
limited to about 1700-1800 v. max.!! (normal svc.)
CARL / KZ5CA
----- Original Message -----
From: "D Conklin" <dconklin@neo.rr.com>
To: <amps@contesting.com>
Sent: Monday, January 23, 2006 6:36 PM
Subject: [Amps] SB-200 Amp with 811 tubes?
> Gurus,
>
> Amp rookie here.
>
> I got a SB-200 fitted with 2 811A tubes. I was assuming that this was a
plug-and-play replacement for the 572A. A local ham who
> has an extensive but not detailed memory indicates that this was a common
mod due to 811 tubes being cheaper, but that it involved a
> substantial amp mod and wasn't just a plug and play replacement.
>
> I have searched the net for info on modding a SB-200 for 811 tubes and
found nothing. I also searched the QST index without luck. I
> need to know the mod so that i can check if the previous owner (SK) did it
right, or if he completed it - this amp looks like it was
> in the process of being refurbed at the time of his passing - maybe he was
in the middle of converting it to or from 811s.
>
> Any help greatly appreciated - you will go over my head pretty quickly on
this stuff, so talk slowly ;-)
>
> AI8P
>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|