tubes age 143
Date: Fri, 08 Jul 2005 21:15:59 -0400
Subject: [R-390] Ceramic sockets or not?
My yellow striper has several tube sockets in pretty sorry shape. The phenolic
(or whatever plastic-like insulating material it's made out of) is crumbling in at
least a couple of cases. Naturally, the ones deteriorating the most are those in
the least accessible locations (e.g. under the BFO, in-between shielded
compartments, etc.)
I have some phenolic sockets with shield bases already. But I also see that
ceramic sockets with very similar dimensions are available for a couple bucks
a pop. Any opinions on the longevity/durability of these two options? I'm used
to seeing ceramic sockets only where there's a lot of heat, but when the next
radio's owner comes along in a couple decades I don't want him to find that the
30-year old "new" sockets I put in have turned to dust too. The ceramic sockets
with tube bases I've found are the ones in the AES catalog. From the pictures
and numbers they appear to fit in the same size holes and have similar
dimensions.
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Date: Fri, 8 Jul 2005 19:41:10 -0600
Subject: Re: [R-390] Ceramic sockets or not?
I prefer the ceramic sockets myself they are very durable, a parts Viking two
transmitter I had looked like is had been had detonated like a bomb but the
ceramic sockets in it where just fine, once I cleaned all of the carbon off of
them.
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Date: Sat, 09 Jul 2005 09:56:08 -0400
Subject: [R-390] (no subject)
In general, ceramic tube sockets were considered "top of the line." In addition
to being used in high-voltage, high-power and high-heat locations (ie most
transmitter final amplifiers), they were also used in oscillators for maximum
stability because the capacitance between pins changed very little with
temperature. My own 390A has none, and I have not seen any in the odd 390A
modules I have picked up over the years.
"Second best" are mica-filled Bakelite. These are the medium-tan colored
sockets used throughout the R-390A. They were standard for low-power RF
use.
"Third best" are the injection molded black Bakelite sockets. Although these are
below "standard" for the R-390 and R-390A, they are certainly suitable for any of
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