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  1. #1
    Join Date
    Jun 2014
    Location
    Torquay, Devon
    Posts
    495

    Default Positive polarity indicator

    Our P40 has a polarity indicator (Polarity correct when lit) on the main switch panel, which has a burnt out bulb. I want to replace this unit.

    Am I correct in assuming this is 240v polarity?

    20180520_123231.jpg20180520_141233.jpg
    There is nothing half so much worth doing, as simply messing about in boats.

  2. #2
    Join Date
    Jun 2017
    Posts
    701

    Default Re: Positive polarity indicator

    AC doesn't have "polarity".

  3. #3
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,057

    Default Re: Positive polarity indicator

    Quote Originally Posted by sprocker View Post
    Our P40 has a polarity indicator (Polarity correct when lit) on the main switch panel, which has a burnt out bulb. I want to replace this unit.

    Am I correct in assuming this is 240v polarity?
    ITYWF that it is a 240volt neon ( a neon indicator plus resistor)

    You should find something similar from RS component,s or your usual electronic components supplier, for under a quid.

    AC or not everybody knows it as a polarity indicator !

  4. #4
    Join Date
    Apr 2002
    Location
    Cornwall
    Posts
    8,244

    Default Re: Positive polarity indicator

    Quote Originally Posted by penberth3 View Post
    AC doesn't have "polarity".
    Supply live and neutral crossed, normally neon connected neutral to earth, illuminating if crossed giving a live neutral and light on.

    OP's problem looks like a standard neon indicator, as said go to local RS with it.

    Brian
    Kddpowercentre VASR charge

  5. #5
    Join Date
    Apr 2014
    Location
    Kent
    Posts
    209

    Default Re: Positive polarity indicator

    @halcyon, on the Princess 40 the indicator is connected the other way round from your description. The neon lights only when the polarity is correct. Read the label next to the neon on the OP's photo. This is also the case on my P40.

    @sprocker, as others have said and as I can see in the photo, it's a neon bulb with a resistor soldered in series in the tail leads. Neon bulbs tend to flicker for a long time before they eventually fail. If this one failed suddenly it might be worth checking the resistor and connections.
    Last edited by JerryC; 21-05-18 at 18:58. Reason: spelling

  6. #6
    Join Date
    Jun 2014
    Location
    Torquay, Devon
    Posts
    495

    Default Re: Positive polarity indicator

    Quote Originally Posted by JerryC View Post
    @halcyon, on the Princess 40 the indicator is connected the other way round from your description. The neon lights only when the polarity is correct. Read the label next to the neon on the OP's photo. This is also the case on my P40.

    @sprocker, as others have said and as I can see in the photo, it's a neon bulb with a resistor soldered in series in the tail leads. Neon bulbs tend to flicker for a long time before they eventually fail. If this one failed suddenly it might be worth checking the resistor and connections.
    Thankyou all for your replies. I've ordered one from RS.

    @JerryC - The light has been very dim from when we first got the boat, so I suspect/hope that it was on it's way out all along. I will check the connections anyway as you suggest when I install the replacement.
    There is nothing half so much worth doing, as simply messing about in boats.

  7. #7
    Join Date
    Dec 2010
    Posts
    8,505

    Default Re: Positive polarity indicator

    April 5th 2019

    Gentlemen, I'm asking here because my question doesn't justify a new thread.

    I've been given a trickle-charging solar panel which still works...but the identical wires had snapped, so I can't tell which coloured crocodile clip to attach to which wire from the panel.

    Is there a cheap reliable way to test polarity - like, which way a motor will turn - which doesn't require me to buy a multimeter?

    Thanks.

  8. #8
    Join Date
    Feb 2015
    Location
    Conwy
    Posts
    3,647

    Default Re: Positive polarity indicator

    LED?

  9. #9
    Join Date
    Dec 2010
    Posts
    8,505

    Default Re: Positive polarity indicator

    Thank you Bruce...that is definitely the quickest fix I ever had here.

    Even more amazing, I Googled whether LEDs work with reversed polarity, found an old bike light and answered my own question, before I'd read your reply!

    Incredible...I spent 50 minutes on Youtube looking for a way to detect polarity, and there's not one instance of this simple solution.

  10. #10
    Join Date
    Mar 2015
    Location
    Isle of Eigg
    Posts
    6,951

    Default Re: Positive polarity indicator

    Quote Originally Posted by BruceK View Post
    LED?
    Quote Originally Posted by dancrane View Post
    Thank you Bruce...that is definitely the quickest fix I ever had here.

    Even more amazing, I Googled whether LEDs work with reversed polarity, found an old bike light and answered my own question, before I'd read your reply!

    Incredible...I spent 50 minutes on Youtube looking for a way to detect polarity, and there's not one instance of this simple solution.
    If you dont have a handy LED or only one that works both ways....
    Wire the unknown supply in series with a battery. The right way round will light a lamp (brightly), the wrong way round wont (much).
    Just call me Dougal, Sir Dougal to you.

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