[AMPS] Heathkit SB 230 8873 retube options

[nospam4me@juno.com]

re: 8873 in the SB-230  
-
Hello again, 
- 
The big deal about all of this is the Heathkit SB-230 is conduction
cooled. A tube replacement of the same type is a lot less work.  
Modification of the amplifier to a forced air system is a lot more  work 
(vs a new tube swap) and makes it just another  "windy amplifier...."  
- 
I don't think the 8560 is such a practical alternative for this
amplifier. The 8560a/as and 4cx250 tetrodes are not as well suited to
grounded grid operation as the mentioned triodes and tetrode operation 
gets you away from the simplicity of the zero bias triode circuit (no
additional screen and bias supplies required)
- 
Other than a large relay clack,  the SB-230 operates with less noise than
any other amplifier I own except my home brew two-hole version of the
same 8873 tubed amplifier. The large modified Surplus Micor repeater heat
sink is a great place to stay nearby on a cold night...   Just be
cautious of the aluminum type anode version of the 8873...  it crumples
in with much less applied force.
- 
cheers   
skipp  
-
:You might also want to look into another version of the 8873, which is
the
:8874/3CX400A7 triode. It uses the same socket as the 8873.
:No screen supply required.  Modification for air from the bottom is
:required.
:If considering a conduction cooled version of the 4CX250B,
:look at the 8560A/AS (Eimac & Svetlana).
:One of the Svetlana low cost tube sockets (SK2A @$10) should mount
easily.



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