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Zener dioide connectivity?

Discussion in 'Norton Commando Motorcycles (Classic)' started by aries, May 23, 2011.

  1. aries

    aries

    Joined:
    Oct 14, 2009
    Hi
    I have a single phase RM 23 alternator stator with 3 wires. Apparently these require two zenor diodes be used. Can anyone guide me how the second diode needs to be connected up please. Thanks
     
  2. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    [​IMG]

    On the 850 Mk3, the second Zener is fitted to the D/S Z-plate.
    Note that the 850 Mk3 RM23 also uses a half-wave 49181 (2DV 406) bridge rectifier, and that each Zener connects to a stator output wire on the AC side of the rectifier.
     
  3. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    I just noticed, if it's a 3 wire stator then it can't be an RM23 ?
     
  4. Josh Cox

    Josh Cox

    Joined:
    Sep 24, 2010
    Could you post more information, photo ?, the instruction on the unit ?.

    Generally speaking you can hook two Zeners in parallel to share to load ( or use a higher capacity heat sinked unit ).
     
  5. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    You can, but the two Zeners are then supposed to be a matched pair-if they are fitted in parallel on the DC side.
     
  6. Josh Cox

    Josh Cox

    Joined:
    Sep 24, 2010
    True, beta matching is often important, but we are not working on the space shuttle here. :D
     
  7. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    Nevertheless, the high output alternator (RM24) kits were normally supplied with a matched pair of Zeners.

    http://www.oldbritts.com/17_333131.html

    It was also recommended that the Zener wires should be approximately equal in length.

     
  8. aries

    aries

    Joined:
    Oct 14, 2009
    Hi All
    Yep, I got cofused about the RM 23. This is a single phase 3 wire, numbered 47174, fitted some years ago to my 1972 commando. Concerned that overcharging will cause problems elsewhere. I cannot remember which diode of the rectifier the second matched zener connected to. Cant get my head around electrics and may be easier to buy a power box!!.
     
  9. L.A.B.

    L.A.B. Moderator VIP MEMBER

    Joined:
    Nov 20, 2004
    So I'm guessing two of the three stator output wires (Green/Yellow/ and Green/Black?) are connected together, and then connect to one of the AC terminals on the rectifier, and the third stator wire is White/Green(?) which is connected to the other rectifier AC terminal (the AC terminals are the outer spades on the Lucas single-phase rectifier and the DC ouput is the centre spade terminal)

    If so and you have a matched pair of Zeners and a full wave pre-850 Mk3 Lucas rectifier then the Zeners can both be connected to the DC output wire-which is usually Brown/Blue on a '72 model.
     
  10. aries

    aries

    Joined:
    Oct 14, 2009
    Thanks for all your input. Try to retain some originality, but have decided to go with a power box. Now gotta figure where to stick it on the bike!
    Cheers.
     
  11. Jeandr

    Jeandr

    Joined:
    Jan 22, 2008
    Wise decision :wink:

    Jean
     

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