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Neon Lamps In Vintage Radio

Discussion in 'Electronic Basics' started by [email protected], Nov 3, 2007.

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  1. Guest

    Hi, not sure if this is the right place to ask, but here goes.. I have
    an old 1960's radio that uses two 6 volt incandescent lamps for the
    dial. Would it be possible to substitute these for NE-2 neon bulbs?
    The side contact on the bulbs connect to the chassis of the radio
    which acts as earth.
     
  2. Baron

    Baron Guest

    Yes! However you would need to disconnect the 6 volt supply and then
    provide suitable dropper resistors from the HT for the neons.
    I can't for the life of me understand why you should want to do this.
    The 6v bulbs are available and cheap enough.
     
  3. Guest

    I want long life bulbs in the radio as it's hard opening the radio to
    replace the bulbs. I could go with LED's if that's easier.
     
  4. Guest

    I forgot to mention that this is a transistor radio, the only high
    voltage is at the transformer. Perhaps LED's are the easy way. Some
    bright orange ones would do. What resistors would I need for them?
     
  5. Phil Allison

    Phil Allison Guest


    ** Use 9 or 12 volt bulbs - you goose.

    Last for a decade, or more.

    NE-2s will never produce enough light.




    ....... Phil
     
  6. Guest

    ** Use 9 or 12 volt bulbs - you goose.

    I thought of that, however as the existing pilot lamps are hidden
    behind the dial and reflect off the clear faceplate, they aren't
    bright enough now, so 12 volt bulbs would be ineffective. I'm
    thinking of going with bright LED's and bringing them around the front
    of the dial for more light.
     
  7. Phil Allison

    Phil Allison Guest


    ** LOL - wot a wacker.


    ** Vintage ones.




    ....... Phil
     
  8. Baron

    Baron Guest

    In which case I would definitely stay with the incandescent bulbs!
     
  9. Chris

    Chris Guest

    Hi, The1930s. A bit of a problem here -- older transistor radios used
    the low voltage AC secondary for the lamps, not DC. That means you'll
    have to drive your LEDs with a series diode, too.

    I'm assuming you've got a 6.3VAC secondary which is driving the
    lamps. Orange LEDs require around 2V forward voltage drop when on.
    If you add a 1N4001 diode in series, you might want to start with a
    220 ohm, 1/4 watt resistor. The end product will be the resistor and
    the diode in series with the LED.

    Good luck
    Chris
     
  10. Guest

    The radio does work without the lamps. I think I will go with LED's.
    I've found a "sunset red" red LED at the Dick Smith Electronics web
    site, but I can't check the voltage because the site keeps crashing.
     
  11. Especially since the bulbs are there to luminate the dial, and neon bulbs
    aren't likely to supply the same amount of light. Their place in things
    is usually indicators of voltage rather than to supply light.

    Michael
     
  12. Guest

    I've been thinking about that, I will check the specs when the
    stupid site lets me. The LED is advertised as super bright, I don't
    won't a dim one, there's no point in that.
     
  13. Guest

    I have some 1N4002 and 1N4007 diodes. Would they work?
     
  14. Chris

    Chris Guest

    Yes. These diodes will all work for the low voltage of the 6V lamp
    socket. A 1N4002 blocks to 100V, a 1N4007 to 1000V. Save the 1N4007s
    for higher voltage if you've got both.

    I should mention that some radios have the incandescent bulbs in
    series, which would mean a 12V secondary. Try pulling one bulb, and
    seeing if the other goes out. If so, you may have a 12VAC secondary.

    As above, a 220 ohm, 1/4W resistor in series with the LED and the
    1N400X diode should work fine if there's a 6VAC secondary. If it's a
    12VAC secondary with the bulbs in series, then make sure to replace
    both incandescents with LEDs, or it won't work. Also be sure all the
    LEDs and diodes are lined up so the anodes are toward the more
    positive side, or it'll be a frustrating experience.

    When you're at the website, look for the "viewing angle" to see if the
    LED light is tightly focused. You probably want a wide angle LED
    here.

    Good luck
    Chris
     
  15. default

    default Guest

    Not without some tinkering with circuitry. A 6 volt incandescent
    requires 6.3 volts nominal at something like 100-200 milliamps to
    light.

    A NE2 or similar small neon requires about 60-80 volts or so to ionize
    the gas and then the current has to be limited to a few milliamps with
    a resistor.

    You might substitute an LED with suitable dropping resistor and a
    rectifier since most OLD toob type radios used AC for the pilot lamps
    - they even make replacement LED lamps with bayonet and screw bases
    with built in resistors - for DC.

    If you are dead set on neon for esthetic reasons it can be done, but
    requires more arm waving and head scratching.

    One thing - does the radio work without the lamp bulbs in place? Some
    of the old AC/DC radios put the lamps in series with the filament
    string of the tubes the lamps would initially come on very bright then
    quickly dim to normal as the tubes heated - without the lamps the
    radio wouldn't play at all or be very distorted and weak sounding.
     
  16. Guest

    I' going to have to stay with the existing lamps. I inspecting the
    radio and there's no way the LED's will fit between the faceplate and
    the dial, without filing a hole in the faceplate, and I don't want to
    do that. Thanks for all your help.
     
  17. Ecnerwal

    Ecnerwal Guest

    You can simply run two LEDs back-to back. If you have enough voltage,
    you can run two strings of two diodes (4 total) back to back with a
    smaller resistor, and get more light for the same power. LEDs are
    current-sensitive devices - the resistor is there to limit the current,
    but the voltage dropped by the LED may vary a bit - ideally, you might
    want to measure the actual voltage dropped by the specific part in hand
    when adjusted to the correct specified current - use a potentiometer and
    a milliammeter, and start with a high resistance on the pot (too little
    current is fine, too much current is a one-time magic-smoke-releasing
    event. Then stuff in a resistor just a bit larger (for a safety factor)
    than the reading on the pot when you have the pot adjusted for the rated
    current. If you have 6 volts, you should certainly be able to run 2 red
    or yellow LEDs in series.

    You might get a better color using a red and a yellow or green. Depends
    what color you want...

    The ones I presently have in stock list a typical forward voltage at
    20mA of 2V and 2.2V, with maximums of 2.5V and 2.6 V - so if you have
    6.3V available, pick a resistor to drop ~2V at 20 mA and it should work
    to drive 2 in series. ie, 100 ohms, for that example. Your parts may
    vary - typical circuits are designed to underdrive the LEDs to keep them
    safe with part variations (ie, 270 ohms from 5 volts in series with a
    single LED.)

    6.3VAC~--------
    |
    \
    /
    \ 100, 110, 120 Ohms (progressively dimmer and safer)
    /
    |
    -------
    | |
    \/ -- Back-to-back LEDs
    -- /\
    | |
    |------| (connection here keeps reverse voltage low)
    | |
    \/ --
    -- /\ Back-to-back LEDs
    | |
     
  18. default

    default Guest

    Red LEDs require about 1.8 - 2.3 volts to light and most standard
    size - 20 milliamps so would require a dropping resistor to limit
    current, as well as rectifier - many leds only withstand a 5 volt
    reverse voltage before they self destruct.

    But check the specs.

    When they specify light intensity in millicandellas or mcd that is the
    light output in a specific area of the target - the beam width and
    intensity have to be considered. The light of an LED is directional -
    something to consider when replacing incandescent's with leds.
     
  19. Ken

    Ken Guest

  20. default

    default Guest

    Well - there's all kinds of leds today. I have a few in my MC tail
    lamp that are rated in lumens, dissipate a watt each, and have a 120
    degree beam spread.

    Overkill for a pilot lamp.
     
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