[Amps] Heath SB-230 conversion?

Wed Sep 17 23:40:17 EDT 2003

Eric, et. al.,

The same tube with forced air cooling is the 3CX400A7/8874.  It has same
filament, heater, socket, plate cap, etc. as the 8873 used in the SB230
amplifier.  If you can move the socket forward a little or bump out the back
when removing the heat sink to have the cooling fins clear the back panel it
will fit.  This tube has a diameter of 1.64 inches, same as the 8873, but
without the flat spot.  See Eimac page:
http://www.cpii.com/eimac/catalog/167923.htm

Alternately if there is a little more room you could substitute a 3CX800A7
tube which has twice the dissipation.  It requires more space, as it is 2.53
inches diameter.  It uses a 13.5 volt filament, so another transformer will
be needed.  I am told this tube runs well on 12.6 volts, so a common 6.3
volt transformer in series with the existing 6.3 volt supply should work.
See Eimac page: http://www.cpii.com/eimac/catalog/16964.htm

The original tube (8873) and both of the above tubes use the SK-1900 socket.
Roton makes a 22 cfm cooling fan that is about the right size, same as a
muffin fan, but with a 2.1" x 0.94" air output port.  Model number BT2A1.
It is listed in the All Electronics catalog:  www.allelectronics.com
part # CF-119.

Good luck,    George    K8GG

----- Original Message -----
From: "Eric Lowell" <elowell at maine.rr.com>
To: "Amps at Contesting. Com" <amps at contesting.com>
Sent: Wednesday, September 17, 2003 7:38 AM
Subject: [Amps] Heath SB-230 conversion?

> Folks,
>
> Does the SB-230 lend itself to (relatively simple) conversion to a more
> available tube?
>
> Thanks, Eric (W1EL)
>
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