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NE3 neon bulbs in antique meter-what are they for?

Discussion in 'Electronic Basics' started by Eric R Snow, Feb 11, 2006.

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  1. Eric R Snow

    Eric R Snow Guest

    Greetings All,
    I was given an old meter that was originally bought by the US
    government. It was missing some labeling so I don't really know yet
    what all it can do. It can measure some kind of radio signal (I think)
    because it has a probe that connects to the kind of fittings I've seen
    on radio gear. The fittings are large co-axial and the probe plugs
    into the fittings. The probe for this has some kind of tube (valve for
    the Brits) in it with a metal point coming out of the end which makes
    contact with what looks like a gold plated piece of bent flat spring.
    I know this is not a very good description and I will be posting
    pictures of it on the web site. This device is about
    6" x 9" by 8" tall. It had gotten wet so I took it apart to dry out
    the internals. The meter movement seems to have stayed dry but other
    stuff inside got wet. Inside the thing are two what I think are NE3
    neon bulbs. The sockets for them are marked NE3. I was able to find
    some on the internet for sale but no pictures. I have two questions
    about these bulbs. First, since any light coming from these would not
    be visible when using the meter what could their purpose(s) be? And
    second, how can these bulbs be re-glued into their bases? I was going
    to remove them from the sockets to clean the contacts in the sockets
    but the glass bulbs are loose in the brass bases. I could buy new ones
    but at anywhere from 9 to 15 bucks apiece, plus shipping, it's too
    much money to spend on something that I don't know will even work when
    plugged in. For that matter the meter is might release all it's magic
    smoke when plugged in the first time. It's interesting that the power
    supply section is made to be swung out when the case is removed from
    the meter. Printed on the chassis inside are instructions to remove
    two particular screws to pivot open the power supply.
    Anyway, thanks for any help and insights.
    Eric R Snow
  2. The neons sound like static protection to the input (They fire on a voltage
    of around 90v each) , mebbe it was used to measure RF ?
    The glass tubes can be glued back into their bases with araldite or similar.
  3. Art

    Art Guest

    Any way to post a photo of the device, maybe we could identify it a bit
    easier, thx
  4. Bob Masta

    Bob Masta Guest

    I've also seen this neon threshold exploited for use as a voltage
    regulator. And because it takes less voltage to maintain the
    discharge than to start it, neons were sometimes used to
    make simple relaxation oscillators.

    Best regards,

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    Home of DaqGen, the FREEWARE signal generator
  5. Eric R Snow

    Eric R Snow Guest

    Thanks to all of you who posted answers to my meter questions. I will
    post pictures on the web site in a couple days. I'll
    post the link here when they show up.
  6. Sounds like an R.F. millivoltmeter. The probe containing a rectifier diode
    type valve that gives a DC out proportional to the RF voltage at the
    With small RF signals, the DC out may only be a few mV and could be the
    reason for the neons.
    They are possibly used in conjunction with a couple of CdS photocells to
    'chop up' the DC (at a low frequency) to allow easy AC amplification and
    finally drive the meter.
  7. Eric R Snow

    Eric R Snow Guest

    Greetings John,
    Your description matches this device. It has mills, DC, and Ohms. The
    NE3 bulbs do not have any CdS photocells associated with them. I
    powered up the device and only one of the two neon bulb lights up.
    There tubes, I think electrolytic capacitors, and one power
    transistor in this thing. Do you know if it would be worthwhile to try
    to make it work again? The meter movement itself seems fine. Is it
    maybe something that a radio person could use? And is worth the cost
    of shipping? It is just a curiosity to me.
    Eric R Snow
  8. Eric. G'day.
    Sadly, I'd say it sounds like it's a junker. Great value and benefit in
    it's time but now outpriced, outperformed, outgunned.
    The neons look like they're there as voltage stabilisers. Beyond that, the
    meter is the only bit worth saving.
    Over the years I've found I can't even give this kind of stuff away and had
    to scrap tons of it.
    All of it magnificently engineered, using the finest materials and doubtless
    classics in the making. Would need though a secure warehouse and another 40
    years of careful ageing and TLC :)
  9. Eric R Snow

    Eric R Snow Guest

    That's what I thought. It has a really nice bakelite case. Maybe I'll
    keep that part if I can't find someone who would like the whole thing.
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