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Old 06-23-2011, 09:53 AM
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miniman82 miniman82 is offline
First Light: 1952-2011
Join Date: Jun 2009
Location: Great Mills, MD
Posts: 4,118
Originally Posted by John Folsom View Post
But I a certain it the the youngest of the metal bell prototype tube identified so far, due to the 3 bolt faceplate mounting and the fact that the mu-metal shield is an external component. I believe the C73293 and C73547 series tubes had an internal mu-metal shield incorporated into the design.

Another wrinkle, then: mine has an external shield, which sits on the plastic (capacitive?) insulator.

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