[ARC5] Your deaf receiver.

[Richard Knoppow]

    I think it was suggested that he investigate the wiring to see if 
its been hacked. If it has there may be other hacking.  A good visual 
inspection is in order.  If brian does not have a tube handbook several 
can be found on the web, for instance at www.tubebooks.org   I think he 
has RCA, GE, Sylvania.  Some more at bunker of doom site.

On 9/27/2016 12:16 PM, AKLDGUY . wrote:
> Brian cannot be using a 12SF7 in his BC-454. The pinout for the 12SF7 is
> so vastly different from that of the 12SK7 that even the heater pins are
> different. But he has already told us that all tubes heat up to normal
> temperature.
>
> So a 12SF7 cannot have been fitted, unless some hacker has wired the
> heater pins for 12SF7 and messed up the wiring of that socket's other pins.
>
> 73 de Neil ZL1ANM
>
>
> On Wed, Sep 28, 2016 at 3:40 AM, Kenneth G. Gordon
> <kgordon2006 at frontier.com <mailto:kgordon2006 at frontier.com>> wrote:
>
>     The 12SF7 is ONLY used in the AN/ARC-5 receivers at the 2nd IF, and
>     its base diagram is
>     very different from the 12SK7. Plugging one into a BC-454's, or an
>     ARA's, second IF stage
>     will "confuse" many of the connections in that stage.
>
>     If a 12SF7 is being used in this BC-454, it is no wonder the gain is
>     down!!!!!
>
>     The 12SF7 has an added diode inside the tube. This is where the AGC
>     voltage is taken off
>     so that the BFO can be either on or off without effecting the AGC
>     circuit.
>
>     The AGC circuit in the AN/ARC-5 receivers was much improved over
>     that in the earlier
>     receivers.
>
>     Ken W7EKB
>
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL