[Hammarlund] Tube Shields?

[Richard Knoppow]

       Its also often the case that the bottom part of the socket, that 
is the part the shield fastens to provides sufficient shielding around 
the leads where it is often most needed.


On 2/11/2015 6:27 PM, Roy Morgan wrote:
> On Feb 11, 2015, at 7:19 PM, K3PID <Ron.K3PID at sbcglobal.net> wrote:
>
>> What possesses someone to open a nice vintage receiver and take out all the tube shields?
> Perfectly good question, which has at least some good answers. This has been one of those recurrent topics on the R-390 list.  My comments are taken mostly from there:
>
> - It was well established (in studies by tube and equipment manufacturers and by the military) that normal tube shields measurably raise the tube operating temperature.
>
> - Tube envelope temperature is one of the primary factors associated with shorter or longer tube life.  Cooler tubes last longer, sometimes much longer.
>
> - In military and mobile equipment, tube shields were often installed to keep the tubes seated in their sockets where vibration and shock were expected.  Your HQ-180 is unlikely to see such conditions.
>
> - In the R-390A receivers in particular, only a few of the tubes needed shields to reduce spurious signals within the radio.  Maintenance instructions were issued to remove all the others.
>
> Based on the above:
>
> - Having no shields may be a good thing.
>
> - If you find and install replacement shields, you may decide to stock up on spare tubes.
>
> - The presence of spurious signals in the HQ-180 due to lack of shields is an unknown.
>
> - Based on pictures I have here, it appears that the shields in the HQ-180 may not be the normal shiny, nickel plated ones that fasten with a bayonet type socket ring, but may be held in place by spring fingers at each socket.  The more common bayonet type may or may not fit right.
>
> - Avoid running your HQ-180 in tanks, jeeps, or Navy carrier aircraft.
>
>> My HQ-180 has NONE, NADA, ZIP shields!
> The tubes in your radio *may* well be better off.
>
>> Anyone have one, some, or all of the shields for said receiver?
> Sorry, none where I am now.  You may be well advised to search for the IERC type black thermal conducting type.  You may pay more for a set of those shields than you did for the radio.  Adding a small fan to your radio would also help a lot.
>
>
> Roy
>
>
> Roy Morgan
> RoyMorgan at alum.mit.edu
> K1LKY Since 1958
>
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL