[Boatanchors] Question

[rbethman]

Al,

In days of OLD, 1943?  Sometimes there was a metal shield underneath the 
socket that was attached to the mountings screws of the socket to 
provide for this shielding.

I've seen this as the norm in old Navy receivers, such as the RBM 
series, which used 12SK7s and the like.

Bob - N0DGN

Al Klase wrote:
> Hi Gene,
>
> Inserting questing, especially so as we werejust  pondering the internal 
> shields in the middle of octal tube bases just this morning on the 
> milsurplus reflector.
>
> The continuing struggle in high-frequency amplifiers is to reduce the 
> usually degenerative capacitive coupling between the plate and grid 
> circuits.  The screen grid takes care of this inside the immediate tube 
> structure, but thre's still coupling between the leads.  If you look at 
> the base diagram for a typical RF tube, like a 6BA6, you'll find the 
> signal grid and plate are on opposite sides.  Placing a grounded object 
> in the middle of the socket reduces the unwanted coupling.
>
> Al
>
> On 2/18/2010 2:15 PM, WØQFC wrote:
>   
>> While rebuilding several old rigs and test equipment I have noticed that the
>> instructions say to ground the center post of the 7 or 9 pin tube sockets.
>>
>> Is there any reason for this other than a convenient point to route the
>> ground wire(s)?
>>
>> Any thoughts????
>>
>> Gene, WØQFC
>> Spring Hill FL
>>
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