What the heck are these darn things??

[A-Barr]

Howdy y'all,
My mother just gave me an old cigar box of my grandfather's labeled "Radio parts." He was a physics professor and a tube DIY'er, he died a couple of years before I was born. Anyway there's some cool stuff inside - a couple Mallory and Astron PIO caps, a filter choke, a couple recitifer tubes and dozens of these funky little christmas light-looking things.
They are about an inch long and maybe 3/8 wide. There are 2 leads coming out of each one and they connect to 2 identical little metal poles inside the glass "tube."
I thought they were light bulbs, but the 2 plates do not meet and have no filament! Magnetic switches? Passing a humbucker over them while hooked up to a meter does nothing. They appear to have infinite resistance but each time I swap polarity of the tester, the resistance starts low and then quickly ramps up, like a capacitor. BUT they do not pass audio and have no markings on them!
...I would post a pic, but being the tech genius that I am, can't figure out how. Anyone have a clue what these are?
Thanks!

[Scodiddly]

Sounds like neon light bulbs. Typically you'd put a small resistor on one of the legs and hook it up to 120vac. I guess LEDs have killed neon bulbs off, but you used to find them in panel displays and especially on power stuff.

[djimbe]

Yeah, likely neon, as Scodiddly says. I have two tube organs that are loaded with them. They're used as troubleshooting devices. For example, each of the foot pedal contacts has a neon bulb attached to it. Push on a pedal, and when it makes contact with the buss arrangement (sending signal to the tone generation system), the neon bulb lights up as an indicator that contact has been made. Every key, stop, voicing, etc. on those organs has a neon bulb (one or more) connected in the circuit somewhere. The back panel is something else. Dozens of those things, all winking on and off as you play the organ...

[A-Barr]

That is pretty cool, I'm always amazed at how much electronics they were able to cram into those old organs. I was thinking about wiring these up into something, but using neon bulbs just sounds like I'm asking for noise problems.
Thanks, guys.

[philbo]

That is pretty cool, I'm always amazed at how much electronics they were able to cram into those old organs. I was thinking about wiring these up into something, but using neon bulbs just sounds like I'm asking for noise problems.
Thanks, guys.

Nah, these won't generate any appreciable noise. You're maybe thinking of the big neon signs that run off 12000 Volts. These turn on at about 90V, with very low current - maybe 10 mA.
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[ciminosound]

Little neon bulbs like that were used with LDR's in Fender amps for tremolo forever. I used to have an Ampeg VT40, early 70's production, that had neon instead of bulbs for standby and power lights.

The neon bulb doesn't generate the noise anyway, it's the ballast/transformer that does. The newer type of mini fluorecents that use the switching power supply are LOADS quieter that the old shoplight variety too.

Funny just like in Audio, want quiet, use a well filtered regulated supply and problem solved.

[Dan Kennedy]

Well to some extent.

Nowadays the ballast in a flourescent lamp for office use is up in the just above audio range, so it's merrily humming away putting out 25kc of crap, instead of the old 60c stuff it used too. Just as much, you just can't hear it.

Gets into bloody everything, makes it a pain in the ass to measure stuff. My gear is fine, but setting up voltmeters and stuff so they ignore it is a pain.

Imagine how much of it is getting into your A-D's and you don't even know it...

[A-Barr]

Imagine how much of it is getting into your A-D's and you don't even know it...

Not if you're only using a 48K sample rate!

...right?

[brianroth]

Low-level mains garbage can leak into ANYTHING...analog or digital, and sample rate has NO bearing on the possible/unwanted results <g>.

Bri