[ARC5] Restoring rusty metal tubes

[Leslie Smith]

Thanks to those who replied so far.  I will pick a 'donor' tube and wire a
primitive test rig.  I don't have a real tube-tester.  I figure tubes are
much tougher than we often imagine.  I think that tube living in a B-17 (or
whatever - full of vibration) for many hours were tough.   I don't know if
the command sets lived in PBYs, but that may be even more demanding.
(Maybe the 'tubes' wore ear-plugs.  That way life would more pleasant.)

I don't think I can save the marking on some tubes - but if I can get an
elegant polished black tube with hand-written ident - I've got something
better than what you see in the snapshot.  The snapshot is true to life.
(Hope it comes thru)

After testing I will give it a working over with a nylon abrasive scrubber
we have here called scotch-brite.  Sheet-metal workers use it for polishing
steel.  Then a metal undercoat and a gloss top coat.  Then some Johnson's
floor-was.

Now I'm going off-topic.  Here is a link to a home-brew regen receiver
project.
https://people.ohio.edu/postr/bapix/Regen_HB.htm
Since the first time I saw this web-page I wanted to try a beam tetrode in
the role of regen detector.
Here is a comment from the link above:
""I did get some difference when I used a 6V6 vs something like the 24 or
6SK7, in that the current through the circuits was higher giving higher
effective gain at low voltages from the beam pentodes as compared to the
normal RF pentodes.I am not why certain power tubes might have been used in
detector service other then possibly as ''power detectors'' where there is
a fair amount of current flowing in the detector to get less square-law
detection."

I may add a solid state "back end" in place of the second tube.  eBay has
dozens of ads for small AF amps.  I bought 2 unassembled kits recently.  I
think some-one must have a 44 gallon drum of LM386 chips they want to get
rid of.   One kit I bought came with LM-386-1; the second had LM-386-M.  In
both kits some holes were too small to take the input jack.  The circuit is
set up for a (voltage) gain of x200.  I reduced that to x50.  That gives
useful volume with 5mV signal in.  (Had to cut a track to do that - but
hey!  That's fine.)  10mW is useful volume and high-Z 'phones are getting
scarce these days.
The tube in a regen set shouldn't get too hot.
BTW, here some photos of a nicely restored AR-7 by McNaughton.
Link:  http://www.macnaughtonart.com/ar7_restoration.htm

Very nice.
Best wishes fr. AU

Leslie
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