Neon indicator connection help please.

Discussion in 'General Electronics Chat' started by Larry4911, Mar 15, 2012.

  1. Larry4911

    Thread Starter New Member

    Mar 15, 2012
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    Hello, I am new to the forum but have been doing my own electronics for some years now.

    I am in the UK and working with 240VAC before anyone gives me advice around 110VAC.

    This is my first time using them and I am a little confused over neon indicators.

    I have also tried searching for previous posts relating to neon indicators on this forum and Google. However, I cannot find anything relevant on this forum and some idiot decided to name a car neon which rather messes up any Google search.

    I am working on a twin deck record player that I have had sitting around waiting for me to replace it's burned out circuits. I have connected 240V neon indicators to show mains and both decks power on/off, between the switch lines and neutral to each switch, as I thought I was supposed to, they are all three, lighting to about 1/2 of full on with the switches in the off position.

    So what am I doing wrong and how can I fix this problem?

    Thanks

    Larry
     
  2. hwy101

    Active Member

    May 23, 2009
    91
    28
    You may have the "hot" and the "neutral" reversed.
    the "hot" goes to the switch.
    Is your plug for the mains polarized?

    You must be extremely careful working with line voltage, always unplug the unit before digging in.
     
  3. KJ6EAD

    Senior Member

    Apr 30, 2011
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    Assuming that you have the right type of switch and it's connected correctly, there is another current path to voltage, probably through a component such as a transformer or diode, but it could be something else or my assumption could be wrong.

    There's nothing magical about the neon indicator itself. It's just a neon bulb with a voltage dropping resistor packaged together.
     
  4. Larry4911

    Thread Starter New Member

    Mar 15, 2012
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    0
    Thanks for your replies.

    I have just found out from the supplier that they are in fact 95volt neons with incorrect stickers applied. So, that is probably the reason for this *&$%^* up. So, how can I fix this?

    And no I haven't reversed any connections and I am very well versed in the ins and outs of mains wiring having been an electrician for several years. But I understand your reason for making that statement. It never hurts to inform the uninformed.

    Will a series resistor be all that is required with this problem? I seem to remember using 1/4Watt resistors while doing my Electrical Installation training with neons in a plug top mains tester we made, rather like I think it was called a martindale tester.

    Thanks

    Larry
     
  5. KJ6EAD

    Senior Member

    Apr 30, 2011
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    Yes, more resistance in series is one way to keep the indicator from failing prematurely but it doesn't explain the presence of voltage on the "off" switch terminal.
     
  6. hwy101

    Active Member

    May 23, 2009
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    A 330k or even a 560k resistor would be suitable for 240V line.
     
  7. Larry4911

    Thread Starter New Member

    Mar 15, 2012
    21
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    OK! Found it. It was leakage from the switch suppression capacitors. I used the original ones that were already attached to the switches and probably should have changed them before now. Clipped them off and no longer any leakage problem but I bet I'm going to have a big click on switch on later. Strange I didn't think of that before!

    What size/type of caps should I replace them with because I do want to remove this common cause of trouble down the line?

    Thanks

    Larry
     
  8. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    When you replace them, the problem will most likely recur. Neons run off AC. Capacitors pass AC current. The "leakage" is most likely normal.
     
  9. Larry4911

    Thread Starter New Member

    Mar 15, 2012
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    OH *£$%^*! You are absolutely correct sir. I can only put that mistake down to medication induced memory loss. I knew that, I just didn't connect the dots.

    So, how can I minimise the switch interference/premature failure without leakage of AC?

    How do they do it on commercial products?

    Thanks

    Larry
     
  10. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    How old is this record player? Does it have an amplifier with valves, or is it solid state?
     
  11. KJ6EAD

    Senior Member

    Apr 30, 2011
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    You could try increasing the series resistance. The lamp should only draw a few milliamps. If that doesn't work, you could try using a green neon. Their ionizing voltage is 35 volts higher.
     
    Last edited: Mar 16, 2012
  12. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    I asked about technology because I think that an LED would be better, if the unit has a low voltage DC supply. High voltage (think valve amplifier) is OK too, you would just need a higher wattage current limiting resistor.
    LEDs can be used on the AC side of the supply, but the switch caps might cause them to glow dimly.
     
  13. Larry4911

    Thread Starter New Member

    Mar 15, 2012
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    OK! So, it's not that old. I believe it is a 70's cheap unit. It has two mp60 3 speed decks so it cannot be a high end unit. I'm really only rebuilding it for education and boredom fulfilling purposes. The burned out circuits are early solid state and possibly homebrew stuff. The tracks are not very well defined but the boards are very dense and compact so I'm not too sure about the provenance of the circuits. They could have been 70's kit circuits or the ones you used to get offered in the electronics magazines I suppose.

    As for the low voltage LED option. Yes, that is something that I could have done, and possibly should have done. I didn't think about it at the time and have already drilled the new fascia for the neons. Having an indication of the mains switch for power "on" would not be a problem but then there would be the indication for each decks power "on" which would have been a problem. I would have had to include relays or large resistors for each LED for the decks mains power indicator which would have added both cost and complication. I have a couple of low voltage circuits in it already, for the LED bar graph units I built for each channel and for the mixer which I have yet to build or even start designing. But over all I think I like the appearance of the neons more than LEDs for this age of equipment. It just looks right to me. I know your going to say I have already used LEDs in the bargraphs but that's how they did it in the 70's so no harm, no foul.

    As for valve equipment. The only piece of valve equipment I own is an old RF/AF signal generator I picked up cheap from eBay a couple of years ago. It is not very stable in RF frequency and the AF side is very quiet so I use my sound card for most AF signal generation but it does the job just about.

    Thanks for your comments guys.

    Larry
     
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