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Hamfest booty

Posted: Wed Jun 12, 2019 6:36 am
by Rich Feldman
In May I finally went to Electronics Flea market in Sunnyvale, prepared to sell and give away stuff. Great success in de-acquiring things that were big and in the way, and/or no longer interesting enough. Bought a cool thing or two to make up for the loss, but can now only remember the 1500 watt incandescent light bulb with mogul size base ($5). Now I have two, and am considering art concepts around them.

No time for that in June, but I took it easy on the buying.

Got three loudspeaker woofers with huge ferrite ring magnets, for free.
All bore signs of abuse: one broken cone, one broken spider, and one open coil.

Got a few meters that had interesting scales and/or appeared to have radium paint. $1 to $2.50 each. Plus a clockwork time switch that probably _is_ one of the 10 or 20 that I sold at the same venue a few years ago.
A red CRT "lamp" from rear projection TV, with optical interface but no deflection yoke, free from one of the meter sellers. 2 megohm ceramic tube resistor for $5.

Re: Hamfest booty

Posted: Wed Jun 12, 2019 6:51 am
by Mark Rowley
Nice haul!
I was there last month and picked up a couple of those resistors as well as a large quantity of Swagelok fittings. I heard from someone else who went this sunday and picked up a scintillator, Hysol 1C, and some other items similar to those aircraft gauges. Now that they disallow a bunch of the old computer gear, it seems to be getting better. I'll try again next month.

Mark Rowley

Re: Hamfest booty

Posted: Fri Jun 14, 2019 6:55 am
by Richard Hull
Going to the big Manassas, VA fest this Saturday. I'll report on it. I'll be buying and selling..

Know how to tell radium dials in such WWII surplus and some Korean conflict stuff??...Advice follows, if you don't have a counter....The "good stuff" will have hands and face markings that are NOT white or GREEN, but instead are off-white or cream color, brown-cream colored or dark brown. The more brownish the better. You are sure they put a lot of radium in that meter's paint as, over time, the radiation has horribly burnt the phosphor and paint content to the point of no longer scintillating at all. HOT!

Green is totally out even if it glows brightly with the lights turned out as it is a light activated phosphor! Sorry, no rads here...

My guess is that Rich has 3 hot meters. The two bigger round meters and the small square one at the bottom.

DO NOT take these meters apart!!! Some paint may have micro flaked off over the years. Remember, 1 microgram, (you can't see it), is the maximum internal body burden for Radium!!!!! Super Nasty! Needless to say, do not buy or handle such meters if the face glass is cracked or missing! Store your finds in an old ammo can with those nice mil spec. rubber gasket seals in a non-living space such as a garage or out building. Use the meters as is (sealed) for a great gamma ray source for discriminating out gammas from neutrons in electronic neutron counter setups.

No radium is found in any instruments after the mid sixties, Vietnam or later. Same for watches and clocks after 1970. Alarm clocks of the late 50's and 60's that are radium painted have far less radium in their dials than those made prior to 1950.

While these WWII aircraft instruments can still be found at hamfests, gun shows, etc., they are now considered collectibles and are often priced accordingly. Only at some rare hamfests will you wander into an old box full of meters and locate a gem for $2.00. Folks restoring old war birds gobble up WWII aircraft instruments. They are just getting very tough to find now.

Most hamfest metering is from old WWII military radios and electronics gear that some old ham scrapped out in the 50's....They moldered away in old cigar boxes until he died and are regularly offered in some "silent key" sales tables at hamfests. The widow calls his local ham club to clean out his basement "shack" to sell his electronic junk....The widow gets the proceeds from the club.

That's my story and I'm sticking to it...cause I know these things.

Richard Hull

Re: Hamfest booty

Posted: Sat Jun 15, 2019 1:30 pm
by Jim Kovalchick
I will add to Richard's advice about radium storage. It is difficult to seal the radon daughters in. They get everywhere. At one time I had some watch hands and a couple other radium pieces in a sealed tub that I kept closed for more than a few months. One day I opened it to use one of the sources and found that the lid to the container was screaming hot. I contaminated my hands just opening it. I had to rub olive oil into my skin followed by soap to get my hands back to background after multiple attempts with soap and water alone failed. The counts would have been gone in a day on their own, but I would have had some explaining to do at work if I still had some.

Re: Hamfest booty

Posted: Sat Jun 15, 2019 10:28 pm
by Mark Rowley
It’s scary to think of all the haphazard things folks have done with radium. A recent story involves a friend who nicely warned the proprietor of an antique shop about an open faced radium meter on an old military radio. Instead of following the proper advice that was given to him, the shop owner scraped it all off with a razor and onto the floor and nearby shelf. One can only imagine the activity on his hands when he went home to eat dinner. Not to mention the mess left in the shop.

Mark Rowley

Re: Hamfest booty

Posted: Sun Jun 16, 2019 5:21 am
by Richard Hull
Both Jim and Mark give good advice. When I open an ammo tin in which is stored instruments or even U ore, I always take the tin outdoors to open it.I wear disposable latex gloves to avoid daughter pick up as I lift out the specimens or meters.

I typically let the freshly opened container sit on the outdoor table for about 5-10 minutes to have the radon drift out before removing any items I plan to use. I often do a wet wipe of the interior of the tin to see what kind of daughter activity clings to the walls. However, the bulk of the super hot daughters will be gone in 15 hours or more via their rapid decay. Remember, the daughters are not bits of hot stuff on the inside of the tin, but individual hot atoms only!! Millions and millions of them. They will reside in the pores of your skin and are often quite proof against casual washing, as Jim notes.

An example: If you get 50 million atoms of hot daughters on your fingers and hands, a simple washing might get 10-30% and drive the remainder deeper into the dermis. Brushing and scrubbing can get another 20% and a repeat might get another 20%, but you will note that it is a bit like the decay chart itself, in theory, you will never get it all. Wear gloves to avoid virtually all contamination within the dermis. If you are forced or decide to actually handle ore or unload and repack a storage container with your bare hands, you should read your hands before and after washing using a good 2" pancake GM system before sitting down to eat.

As Jim notes, olive oil is a good start as it can pick up and retain such material prior to washing with a good soapy lather. I have reduced my count by well over 60% on the first oil/washing. A rough and strong soapy brushing will often satisfy me that I have almost returned my hands to near background.

The younger you are, the more careful you have to be. For us old folks we can be more cavalier as nothing would metastasize before we aged ones take the dirt nap due to minor acute doses or even chronic light doses. (I assume all here understand, at a core level, the difference in external acute and chronic doses)

I will admit that I hate the (NLT) "no lower threshold" concept and laugh at the ALARA folks. I give high credence to the hormesis concept due to low level constant external gamma fields. None of this applies here as we are talking about issues that might result in possible inadvertent ingestion of alpha and beta emitters.

Just use good practices.

Richard Hull

Re: Hamfest booty

Posted: Sun Aug 11, 2019 3:55 am
by Rich Feldman
Sold last month, scrounged lightly today. The guy with 12" yellow LED traffic signals was tired of selling them, and gave away the last 10 or 15. Unsurprisingly, this has a narrow viewing angle, and is very bright on axis.
I got a box of old vacuum gauges, and a two-pipe coolant feedthrough, for free. Might have paid money earlier, had I remembered which thermocouple types have better resolution at 20 microns than Convectrons. The one with large box has a sticky label that includes pressure-to-microamps table, and says the heater current should be a standard value plus a calibration value stamped on the tube.
The three tubes on right side of picture have permanent magnets, and a loop of wire inside between the magnet poles. Anybody want to tell us about those?
Paid $2 for yet another battery tester, and $2 for a video camera with lens (and tangled-up 75 ohm BNC cable).
The unexpected $3 treasure (since you all know I like odd lamps) was hiding in a tray full of vacuum tubes. I saw the number 70, above GE logo. Not till home could I clearly read the characters at base level: NA-1.
Figured it was some kind of lamp, with shrouded coiled cathodes top and bottom. Probably sodium, because the condensed metal deposit was solid. Didn't take long to confirm both guesses on the Internet, which I don't do in the field. ... %20NA1.htm It's a stubby version of an early Low Pressure Sodium streetlight, made as a laboratory light source. The filaments in my specimen conduct as expected. Now I need a 4 amp, 6.5 volt ballast (12 volt transformer and incandescent lamp in series?) and a thermally insulating sleeve -- like the clear glass vacuum dewar and asbestos washers in original application.
Anybody know about backing off on filament heating when the lamp is warmed up? My contemporary SOX180 LPS streetlamps have coiled cathodes with no I*R preheating.

Re: Hamfest booty

Posted: Sun Aug 11, 2019 5:07 am
by ian_krase
I went there as well. Sadly, I had not even the slightest luck finding anything that interested me vacuum-wise -- the closest thing was an electron gun controller, but it was an entire 3U (or larger) rack mount box, had no data, and looked sketchy as to where all the outputs were. That, and some random small KF tubing bits that were of little value.

(why doesn't anybody make those in NIM scale?)

Re: Hamfest booty

Posted: Sun Aug 11, 2019 8:01 am
by John Futter
Those three tubes look like crossfield ion gauges ie early penning tubes
came with Noah on the Ark

Re: Hamfest booty

Posted: Sun Aug 11, 2019 10:47 am
by ian_krase
Now that's interesting.

I smell ion source material... Would be very interesting to mess around with one of those.