tubes age 188
I have many of these (along with lots of other JAN 6BA6's/5749W's) I think and I
have never really noticed microphonic problems. I'm starting to think that you're
much more picky than me :-).
Mine say "JAN 5749W Philips ECG 34167 USA" with stamps like "8726 ADE for
date and ?plant?" etc, blue lettering. They often show up at hamfests etc.
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Date: Fri, 25 Aug 2006 13:34:31 -0500
Subject: [R-390] Re: [Boatanchors] WANTED: 26C6 Tubes for R392
Earlier this year he had some NOS 26C6s at reasonable prices.
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Date: Sun, 10 Sep 2006 10:53:26 EDT
Subject: Re: [R-390] Tube Substitutes
<snip> >..........has anyone tried using 6BH6 tubes in the 390 in place of the
6BJ6? .
The 6BH6 will operate. They will change the noise floor. Us them if you have
them they are better than not having a working receiver. There are a lot of tubes
that can be substituted into the receivers. Most of the other stages have so
much filtering and signal gain over noise that a tube here or their will not
degrade performance. If you do not get too many odd tubes into the receiver it
will operate well. I have not found a wonder tube that just gives a better
performance than the stock tubes. Back in 1973 in Okinawa we tried just about
every tube we could get. We found a lot of tubes would work. Nothing popped
up that we wanted to submit the paper work on for a suggestion award. We had
about 60 technicians and several hundred receivers. We were keeping logs
and doing serious alignment and signal to noise test for comparisons. There
was prize money at stake. Most of our operators run with manual AGC so sharp
and remote cut off pentodes did not cause grief. Mostly it was over all signal to
noise ratio. Lots of things worked well at single signal on the bench with a
generator but had lots of noise with a real antenna from mixing of many signals
in the band pass.
There are a lot of tubes that will work well. I have never plugged a tube in
with the correct base match and had the smoke come out. You need to look
under the deck at the actual solder connections. You will find that tubes with the
screen and cathode tied together may or may not work depending on how the
tie is made either in the tube or under the deck. You find only one pin soldered
on the socket and the tube makes up the connection. If you get under the deck
and make up the other pin, a bunch more tubes can be used in the socket.
(14 pages)
(10 pages)
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