tubes age 221
are in such easy supply because of vast quantities of JAN tubes liquidated from
military stocks.
After I got my 390A's, I went out on tube buying sprees snapping up cartons at
hamfests and online; I carried around a "going price" list in my pocket and
made tally marks as I acquired them at lower and lower and lower prices. I got
a lot of tubes for not too many bucks.
I compare the price of tubes today from any of the online distributors to prices I
paid in my hometown 30 years ago, and my conclusion is that I paid way way
too much for tubes back then :-(. I mean, I remember needing 0A2's and
6CL6's and 6AU6's and 6146A's for my Heath radios, and paying an hour or
two's worth of my puny wages for each. I compare it to today where a couple
minutes of my wages will buy any of them.
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Date: Mon, 17 Aug 2009 16:22:05 -0400
Subject: Re: [R-390] Alternative to IERC tube shields
I procured at least a couple complete sets of replacements, including 3TF7s
and 26Z5Ws around 2002. The seller was asking around $40 a set back then.
He threw in some #47 bulbs and some 12VDC auto bulbs that fit the dash of
about 1997 vintage American automobiles. I have one of the Western Electric,
(Made by Hickok - Mdl 6XXX series), tube testers. It performs the conductance
testing along with checks for gassy and shorts. It was an Item I obtained from
a former AT&T employee. He really had no use for it any longer.
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Date: Fri, 11 Sep 2009 19:35:19 EDT
Subject: Re: [R-390] Restoring my '390
I think 24 x 7 x 52 x 5 is a bit long. Tubes will last almost forever but 43,680
hours is mostly over the line. I think Rick Mish got miss quoted. Or lets not take
that exact statement to literal.
Think about 10,000 operating hours on a good tube. For the first 720 -1,000
hours you hope the thing will quite down and get stable. From 1,000 to 2,000
hours you hope it will quite down and get stable, because it did not do it in the
first 1,000 hours. Then you get about 7,000 hours of good tube life. Then the
tube starts to get noisy from what ever its mellow point was.
If you are going to do a PM and change some tubes. Go whole hog and get all
the 6DC6, 6C4's, 5654's and 5759's in the IF string. Swap the in line 5749's off
to the VFO and BFO. Move out any 6AK6's and 5814's that will help get some
noise out of the signal to noise ratio.
(14 pages)
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