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powering 2 LEDS or Neons from a 240v feed?

Discussion in 'General Electronics Discussion' started by cardiffboy22, Sep 10, 2020.

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  1. cardiffboy22

    cardiffboy22

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    Sep 10, 2020
    Hey all! I’m looking to have 2 leds or neons to run from a 240v mains feed. (It’s to illuminate the display of an old 1940s radio.) Can anyone spread some light (forget the pun) on the best way to do this?
     
  2. bertus

    bertus Moderator

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  3. cardiffboy22

    cardiffboy22

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    Sep 10, 2020
    hey there, no not as yet but looking at them I think the brightness may be a little low for the size of the display that needs to be lit. I think I was attracted to the warmer colour lol
     
  4. bertus

    bertus Moderator

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  5. kpatz

    kpatz

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    Most old radios used small incandescent bulbs to illuminate the dials. If you want the most authentic look, that would be the way to go. Are the original bulb sockets and circuits intact? You'll just need bulb(s) of the correct voltage and size to fit in the sockets. Chances are they're fed from a lower voltage secondary of the main transformer, they aren't running on 240V.

    LEDs are best for lower voltage DC applications. They can be made to work on 240V AC but, LED illumination in 1940s radio? I'd rather go authentic and stick incandescent bulbs in there.

    Neon would be easy, just needs a dropping resistor to run straight off the mains, but you'll get a dull orange glow and not the warm white incandescent glow.
     
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  6. bertus

    bertus Moderator

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  7. Bluejets

    Bluejets

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    Dial bulbs used to run on the heater tapping.(6V or 12V)
     
  8. ramussons

    ramussons

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    Jun 10, 2014
    There's a very simple way to use 2 LED's running of mains. Not too sure if the details are forbidden in the forum.
     
  9. Harald Kapp

    Harald Kapp Moderator Moderator

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    If you're hinting at capacitive power supplies: not forbidden but strongly dis en couraged.
     
    Last edited: Sep 14, 2020
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  10. ramussons

    ramussons

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    Is that Discouraged or Encouraged?:)
     
  11. kpatz

    kpatz

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    Encouragely discouraged? Discouraged to be encouraged? I would say, "not a good idea for safety reasons". :)

    In any case, I'd avoid neons for this application, they just won't look good, plus you'd have to run HV to the bulb locations. There should already be low voltage (6 or 12V) to the bulb sockets, so use that, ideally with incandescent bulbs but in a pinch you could use 2700k LEDs. You'd need to rectify the power (full wave is better) and a decent sized cap to get rid of the 100Hz or 120Hz flickering if you use LEDs, and a suitable current limiting resistor based on the desired current and Vf of the LEDs.
     
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  12. bertus

    bertus Moderator

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    Nov 8, 2019
    Hello,

    When using leds, scratch the leds with some sandpaper to have a wider scattering of the light.
    Leds can have very narrow beams.

    Bertus
     
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  13. dave9

    dave9

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    ^ Seems like something good to do to the plastic encapsulated type with the rounded focal dome on top. For those, I take a file or sandpaper on a flat surface and completely sand off the dome to a flat top then polish to clear again, but for the surface mount LEDs none of this is needed, though then you need the PCB to solder them to or if star heatsink mounted, still a more elaborate mount (maybe, depends on the structure behind the area needing illumination).

    The "best" way to do it all depends on the desired outcome. If looking to restore to original state then you should use same bulbs and it's easiest because the design is build around that. If looking for extreme bulb life (why? Surely that old radio can't be such a pleasure to listen to that you have it running all day long?) then you can tap off any lower voltage circuit, rectify and smooth and current limit LEDs. You could even get one of those long, thin COB style so you have less of a burden spreading the light and mounting it, though most of those put several LEDs in series so need a higher input voltage.
     
  14. Harald Kapp

    Harald Kapp Moderator Moderator

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    Discouraged, sorry. Thanks for hinting at this mistake, one never stops learning ;)
     
  15. radio-man

    radio-man

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    Dec 19, 2018
    You can get AD/DC led blubs via on line auction site to replace the standard 6.3v bulbs that were fitted original, I do this in some off my vintage radios
     
  16. DJL33B

    DJL33B

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    Aug 22, 2019
    I think there were some Really Old Radios (this was many years ago, I am almost 70) that had the dial light(s) in the series string of heaters. The dial lights would illuminate slowly as the heater current stabilized. Changing the circuit would be tricky.
     
  17. kpatz

    kpatz

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    Feb 24, 2014
    So if the dial light burned out the whole radio would stop working. Brings a new meaning to "one light goes out, they all go out!"
     
  18. hevans1944

    hevans1944 Hop - AC8NS

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    Maybe @cardiffboy22 could post a schematic diagram of his radio... those are always handy when attempting to restore and/or repair anything electronical in nature.
     
  19. bertus

    bertus Moderator

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    Nov 8, 2019
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