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Neon lamp for turntable repair

Discussion in 'Troubleshooting and Repair' started by Foghorns, May 7, 2016.

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  1. Foghorns

    Foghorns

    3
    0
    May 7, 2016
    Hi,
    Does anyone know where I can get a suitable replacement for one of these?

    Rotel rp-1500.jpg

    Rp-1500 schematic.jpg
     
    Last edited by a moderator: May 7, 2016
  2. duke37

    duke37

    5,364
    770
    Jan 9, 2011
    That does not look like the original.
    You can get very powerful leds which could be supplied from a low voltage winding if you cannot get the original neon.
     
    davenn likes this.
  3. Alec_t

    Alec_t

    2,940
    799
    Jul 7, 2015
    That neon is connected directly to mains voltage if the transformer has the D-type strapping. Having it's terminal(s) exposed as shown in the pic is potentially dangerous.
    Safer to use LED illumination as duke37 says. A pair of back-to-back LEDs (with suitable current-limiting resistor) could connect to terminals 2 and 3 of the power supply.
     
    Last edited: May 7, 2016
  4. Foghorns

    Foghorns

    3
    0
    May 7, 2016
    Thanks for the warning.
    I am a complete novice although I have repaired a few things here and there where i have been given specific instructions as to what to change (capacitors and resistors etc...).
    I'm not using the turntable like this, It normaly has a cover over the lamp which i removed for the purpose of the photo.
    I have read that the LEDs aren't quite as good because they don't flash on and off as well!?

    IMG_20160507_165905258.jpg

    IMG_20160507_170054339.jpg
     
    Last edited by a moderator: May 7, 2016
  5. Alec_t

    Alec_t

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    Jul 7, 2015
    Depends how the LEDs are used. If driven by just the rectified AC they will fade in and out rather than flash briefly.
    LED-fade.PNG
    They can easily be made to flash, however, with a simple circuit like this:-
    LED-pulsed.PNG
     
    Last edited: May 7, 2016
  6. duke37

    duke37

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    770
    Jan 9, 2011
    I would think that if they were fed with a fairly high voltage which was backed off with a zener so that only the peak voltage was used, they would be quite good.
    Could Alec do a simulation?
     
  7. Alec_t

    Alec_t

    2,940
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    Jul 7, 2015
    As requested :-
    LED-pulsed2.PNG
    This shows two alternatives.
    The 'fairly high voltage' duke37 mentions is 10VRMS AC in the sim, since going by the 16V rating of C901 in the power supply, that's what I guess the transformer secondary outputs.
     
    duke37 likes this.
  8. 73's de Edd

    73's de Edd

    3,070
    1,299
    Aug 21, 2015
    .


    Sir Foghorns . . . . . . .

    Possibly . . . .
    Looks like this might be the definitive replacement for that lamp.
    Note that the electrodes are designed for a spot production of illumination, then the lens built into the end
    of the envelope , provides for even further spot concentration.
    It may be a bit pricey, as being compared to a wire leaded common NE-2 (wide lateral/spatial light dispersion) but considering a neon lamps l o o o o o o o o o long life, that would be my choice in a neon replacement.

    Plus you want to confirm that present R901 series limiting resistor value is not being too low for this lamp, if the light initially shows up to be excessively bright..


    Reference:

    http://www.conrad.com/ce/en/product/582852/Barthelme-00012340-Neon-Bulb-230-V-03-W-15-mA-BaseE10-Clear

    Bulb NOT to scale:
    [​IMG]


    73's de Edd


    .
     
    Last edited: May 7, 2016
    Foghorns likes this.
  9. dorke

    dorke

    2,342
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    Jun 20, 2015
    Hi guys,
    A note:
    The neon light in the turntable is used for stroboscopic adjustment of the plate's speed.
    The neon light will "flash" twice in each cycle (both on positive and negative parts),the "bumps" on the plate rim are made in accordance with that.

    Here is a circuit that can replace the neon lamp with 3 LEDs,
    a bridge rectifier and a resistor.
    It will tap into the bridge on the secondary (around 12V peak AC).
    Use a small rectifier bridge, 3 high brightness 5mm blue color 2mA (or 10ma) LEDs.
    for 2ma Blue LEDs use R=1.5K resistor.
    For mounting the LEDs should be glued together.
    LEd-strobe.JPG
     
  10. duke37

    duke37

    5,364
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    Jan 9, 2011
    Alternatively, use another string of leds connected in inverse across dorke's string. Then the rectifier will not be needed.
     
  11. Foghorns

    Foghorns

    3
    0
    May 7, 2016
    Thanks everyone for your very interesting and informative help. However, I'm mostly liking the look of 73's de Edds Neon. I think this would be the easiest solution for me plus it looks like it would fit perfectly into it's housing.
    Am i right in thinking that i should just be able to snip the wires off the old then just directly solder the new one on?
    i.e: it's the correct voltage and ampage rating? ( I said i was novice)
     
  12. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    You can solder the wires.

    There are 2 problems with that solution.
    1. There are so many different Neon lamps with different voltages/currents and light brightness,since you don't know what is the part you have it may or may-not be the correct part.
    2. The lamp body(and bayonet) will be connected to mains so you have to isolate them properly!
     
    Last edited: May 8, 2016
    duke37 likes this.
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