[R-390] Radium dials and 3AT7 'unubtanium" ballast tube--query for the group

[Gregory W. Moore]

Ladies and Gentlemen:

    Forgive me if I bring up a subject (Ballast Tube replacement with 
solid state components) for
probably in excess of 10 to the 6th power (LOL, I couldn't figure out 
how to do superscript in a Netscape web browser), but it does seem as if 
 this is rather a touchy subject, and many modifications have been 
proposed to retrofit R390/A's with other methods for B+ control, etc.

Ok, Query (Flaming, comments, mobs with burning torches parading in 
front of my house are welcome LOL).

Now, here's my proposal:

A. There are one heck of a lot of these fine recievers out there.
B. Oneless one is lucky, most of what is available on the open market 
has had the meter removed becsuse some unnamed environmentalist brought 
up the fact that the original meter dials have a dial
which was made  luminiscent with a Radium (RA-86).  IMHO, there are too 
many environmental zealots running around like chicken little about 
this... Radium is an ALPHA emitter, and since alpha
particles can be stopped by a simple sheet of paper, the dial face along 
with a sealed meter case is
more than enough to protect anyone from what is a "hyped" radiation 
warning.

    Consider that I have spent innumerable hours on watch leaning back 
against one or more R-390(A)'s while in the good ol' USN, and have 
suffered no ill effects, I, personally don't see the problem. Even if 
one were to open the meter case for repair, minimal safety equipment 
would be
indicated (a respirator, latex (or non-latex if you are allergic), and 
some clothes that one wouldn't matter disposing of (not really 
necessary, but in today's world of liberal created "this has got to have 
round corners and dull, non harmful edges" it might be prudent, at least 
the protective mask, and a good source of ventilation with an exhaust 
hose which could be near the work, containing a filter (gause is OK) to 
prevent any dust, radioactive or not, from remaining in the area. forced 
air ventilation might be a good ides (look at an aerospace laminar flow 
workstation for an example).

Now, I am seriously doubtful if the dial is the bad part in the meter, 
the failure usually is something wrong with the movement itself, so 
there is a very infrequent  need to have to actually touch the dial 
face, and if you do, so what, just wash your hands and exposed arms a 
few times, and the problem is gone.

I have done enough rambling for this overdiscussed topic, but it leads 
in to the next, and that is
the power of group purchasing. IF enough of R390philes were to desire 
meter faces, I can't see for the lfe of me why we could not recreate the 
dial via screen printing, using a 600X600 wire mesh screen, or even an 
800 mesh.  One uses an original dial as a template, creates a 4/1 photo 
master at one's drafting table using layout tape and photo imaging for 
the large initial indicia, and reduces it in a process camera. The 
resultant negative is cut to fit a positive location jig which will hold 
the meter faces in absolute position using the cut-out for the movment 
and small drill rod pins for the screw holes, this jig will make the 
dial fit flush with the surface of the dial, and will hold it in 
absolute position.
One then paints the dial with the lightest coat of epoxy or non-solvent 
affected paint, bakes until the paint is cured. At that time, the 
indicia from the screen mentioned above, are screened on to the surface 
(yes, it is necessary to have a 3axis table with micrometer drive to 
line the whole shootin match up, but once the sets are completed, and 
the registration is dead on the money,

My own recommendations, based on my career in aerospace, specifically 
instrumentation design has led me down this path numerous times, and 
when one is subject to nitpick inspection every step of the way, since I 
worked for a NASA cubcontractor, one works any bugs or alligators out of 
the mix early on, and the dials are examined under a 25X loupe or 
microscope, so they better be right.

For Materials, I suggest either Wornow Cat-L Ink� for the white indicia, 
and either the same in flat black (opnote: the black isn't really flat, 
and it is necessary to add a "flatting agent" to the mix in a blender of 
at least a beaker mixer (the one with the magnetic stirrer) to get the 
mat'l significantly flat enough.. For those who are thinking of 
airbrushing matte clear (same mfgr) over time, fagedaboudid
(LOL) the matte yellows (learned during a disastrous period in 1976), 
or, as a much better black,
Dulac Flat Black Lacquer.and if that is also unobtanium. good 'Ol 
Rust-Oleum in flat black is acceptable..You will have to locate the 
Wornow Cat-L- Ink in flat white (FED STD 595) 17875
Use a good screen, mount the jig on a 3-axis table, register, and then 
print to one's heart's content.

Note, if you have an oven specify the heat cure catalyst (The temp has 
to be 80C) but you will find that once you have baked the black it is 
absolutely permanent, without the use of a epoxy stripper such as 
Epco-Strip  (warning, if you splash this stuff on your legs, pour 
vinegar immediately and carefully walk to a decontamination 
shower...this is from personal experience. The red scars look lkind of 
neat once one gets use to them LOL, and this incident was back in the 70's.

Before I go into meters, if anyone would like additional information, 
please email me B/C so the discussion doesn't degenerate into a painting 
and marking thread [huge evil grin).

Once you have gone to the trouble, you are basically in buisiness, and 
are able to produce as many dial faces as one desired, for any meter 
that is needed. The only requirement is what I have named above, and at 
least one dial for use as a template for the artwork,. DO NOT USE THE 
METER FACE ITSELF AS A TEMPLATE, most of the one's I have seen are pure 
scrap, and wouldn't pass any inspection either incoming or outgoing, 
including the Gov't, basically meaning they should have been rejected 
and tosssed back into the bin for complete rework,


OK, nuff about luminous dials, lets talk about the supreme of supremes 
in the class of unobtainum.
I think that we have pretty much in agreement that the 3AT7 ballast tube 
has gone the way of all other good things.. I propose that since there 
seem to be one heck of a lot of  Boatanchrs/R-390 and R-390A enthusiasts 
out there,  I have been wondering if since there are both saftety and 
clout in numbers, that our group en masse could approach a manufacturer, 
be it either here in the good old US of A or more promising, a firm in 
Russia (Svetlana) to produce this tube line again.

    Admittedly, it wouldnt be a billion piece run, but the technology is 
already in existance, as are the manufacturing lines, and since the 
Russian companies are already MAKING hollow state components, I wouldn't 
feel that the tooling for both blowing the envelope, and inserting the 
proper gas for the filler, as well as producing the specialized 
filaments wouldn't be a reinventing the wheel proposition. The only 
pitfalls I can see is (A.) setup costs  which I believe we could 
collectively write off our taxes, and (B.) Dealing with the bureucracy 
as regards to the size of the run...
(C.) At any rate, the patent for those puppies has run out, so the 
manufacture would be in the public domain
If you in the group concur, I would be willing to take over a 
preliminary engineering study oft the feasability of doing so. In 
addition, any other tubes that have become "unobtainum" could be 
handlled in the same fashion. The machines already exist, the basic 
tooling already exists, if not for the exact tube, at least it would be 
in the ball park.. Incidentally, as long as the tube fits, and works as 
designed, the cosmetics of the exterior don't amount to a hill of beans. 
 The only requirement which I would require is the ability of tubes to 
fit an IERC tube shield, so the rig would LOOK
original.

    If anyone has comments, queries, other business, feel free to email 
me off list or on list, and let's kick this around a while and see if 
the idea meets the reality test. I would much rather find out problems 
first, than discover the alligator pits later on..

Your suggestions and criticisms are welcome, FIRE AWAY

73 de ZGreg WA3IVX / NNN0BVN PA

   

-- 
"All that is necessary for the triumph of evil is that good men do nothing."
                                                   --Edmund Burke

Greg Moore NNN0BVN PA
U.S. Navy-Marine Corps Military Affiliate Radio System (MARS)
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