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XS650 Specials - Electronic Rectifier and Regulator Units

Discussion in 'The Lounge' started by Paul Sutton, Jan 27, 2017.

  1. Paul Sutton

    Paul Sutton Sprained Ankle Top Contributor

    I am just looking for some views - Are the original electronic rectifier/regulator units as supplied with the XS Specials considered to be reliable, even some 30+ Years later, or should I be replacing it? What are your thoughts?

    Thank you.
    Paul75 likes this.
  2. littlebill31

    littlebill31 Smells of Raw Fuel

  3. Paul Sutton

    Paul Sutton Sprained Ankle Top Contributor

    Thank you littlebill3.

    I recently replaced the TCI ignition and the rectifier/regulator is the last critical electrical component that is still original. In the past I have read the threads about making your own and I may well do that. Will be checking for available space on the bike this afternoon after I have checked the exhaust valve timing. I understand the differences in regulators (Type A/B) so will do a price check and compare that with a new one from Ebay in UK.
  4. Paul Sutton

    Paul Sutton Sprained Ankle Top Contributor

    $15 - amazing!! In the UK prices are often twice that in the US for some reason? . I have the rectifiers already but the difficulty is determining if the regulators are Type-A. Apart from writing to the Ebay Seller and asking could the presence of a Green wire be an indicator?

    Also managed to find pamcopete's article on making your own rectifier/regulator - Fabulous reading!
    littlebill31 likes this.
  5. Paul Sutton

    Paul Sutton Sprained Ankle Top Contributor

    In the thread "Type A Regulators" 5twins kindly (much appreciated) provided me with a list of Type A circuit regulators for possible use with a DIY regulator/rectifier for my 81 Special:

    5twins said:

    "The usual one used is the VR295. Here's some subs for that .....


    I think these are all basically the same units as the VR295, these are just other maker's part numbers for them. Search any and/or all these numbers on eBay and you should turn up something."

    I have spend many hours searching these out for availability in the UK and successfully cross-referenced this type to a Lucas 14Tr which is readily available for approximately £12 on Ebay UK. It comes in three configurations; 2 wire, 3 wire and 4 wire. The three wire has the following leads:
    • Black B- (Ground)
    • Yellow D+ (Indicator wire)
    • Red B+ Battery positive (Voltage sensor)
    • Metal Casing DF (Connects to field winding to control to Ground)
    Having looked at the XS SH wiring diagram the metal casing of the regulator DF should connect with the Green coming from the field winding and Red and Black are direct colour matches.

    Question: In my reading I have seen the mention of a Surge Protector Diode (a Zener) for the rectifier to protect against surges produced by a loose contact on the field winding i.e. making the alternator produce spikes analogous to the points breaking contact on the ignition coil but not so high a voltage. When I make up my regulator/rectifier unit do I need to add this protection? or is the high 1000V rating of the bridge diodes sufficient? or should I add an MOV spurge protector across each phase wire to ground?

    If I use 5Watt Zeners what voltage should I consider using e.g. 15V, 20V or just something greater than 15V and less than 1000V?

    I am interested in hearing all your views - Thank you very much.
    Last edited: Feb 5, 2017
  6. peanut

    peanut XS650 enthusiast & inveterate tinkerer Top Contributor

    Paul... you've obviously popped a few 'brave' pills and girded your loins for battle with the prince of Darkness:D
    I cannot believe that someone hasn't done a complete blow by blow guide with parts and diagram yet of a diy regulator rectifier
    Might be worth looking on that Oz site

    The only thing I remember about a zener diode on my 68 BSA was that it used a huge heatsink to dissapate the heat of the excess voltage. It had to be sited on the front of the bike to keep cool .

    if you want cheap n cheerful why not replace the original with something like this
    You can buy the necessary electrical plugs / sockets etc on ebay for a couple of quid
    Last edited: Jan 28, 2017
  7. Paul Sutton

    Paul Sutton Sprained Ankle Top Contributor

    Thank you peanut. Those large zeners were used for voltage control and get quite hot - an alternative to a regulator. In my situation the zener is there to pass any spikes greater than the electronics and rectifier diodes can tolerate. These spikes will be very short in time length and very rare so the power dissappated will be very small, much less than 5Watts. I think that something just above the 14.4V should be fine. In all the threads I have looked at I have not seen them mentioned and just wonder if it has been assumed that the spikes will be less than the 1000V tolerance of the rectifier diodes that everyone seems to use.

    Edit Note: Silly me! A zener will act as a short. MOV would be more appropriate over AC.

    I think the origin of the spikes is the power to the field winding and the switching. This would be the situation if the brushes got too short also.

    On your advice I am off to Australia to checkout the threads there - Weather is good in Cardiff, fine but windy.
    Last edited: Jan 28, 2017
  8. peanut

    peanut XS650 enthusiast & inveterate tinkerer Top Contributor

    yep its pretty good here to but my bike is buried in the garage so no chance of a quick blast unfortunately.

    I have been doing a bit of research myself since you posted as I may upgrade my own stock reg rec this year.
    i read Hughs guide and also Petes on his DIY solution .
    To my mind we might as well just take a fully built encapsulated regulator rectifier used on some of the modern 650,750.850,bikes around. it does exactly the same job on all bikes. you just need to make sure it can cope with the load you have on your bike ie electrically heated seat and gloves and TV CD headunit, GPS etc :)

    The trick is finding a circuit diagram so that you can see which wires on the new reg/rec connect to which wires on our XS650.
    Obviously the three white wires from the replacement Reg/Rec are straightforward.

    Then you'll need to connect one of the other wires to the red wire which is fed from the battery via a 20A fuse. (This also supplies the ignition switch)
    The second wire needs to connect to the green wire that goes to the inner stator brush
    the last wire needs to connect to the brown wire which goes to the other side of the ignition switch . The brown wire is a switch live wire which feeds the reg/rect when the ignition is switched on wheras the red wire from the 20A fuse is constantly live from the battery.

    Whichever rectifier regulator you choose there should be a specification and electrical diagram available for it to show which of the 3 wires connect to the three wires on your connector
    Last edited: Jan 28, 2017
  9. Paul Sutton

    Paul Sutton Sprained Ankle Top Contributor

    Peanut, a lot of sense in what you suggest. I will keep track of the costs and compare to a replacement part. Typically they are approximately £70 for the Specials on Ebay but I have seen one supplier at about £55 - But I do not know their quality. In the US there is more $ advantage to make your own because the components are about half the UK cost. I can do this for £27 because I would re-use the connector and already have a heat sink available. But, if I buy a £55 unit on Ebay I will be left with a fully wired spare to carry on long trips - so It's a difficult one for me.

    Looking at the rectifier/regulators for other makes of bike looks at first glance that there is money to save, but they seem to have a different number of wires and I would have to buy the correct connector to make it fit. If you find something interesting let me know - thanks.

    Back to DIY - On the XS SH I need the Type A regulator which is the Lucas 14Tr and this one switches between the field winding and ground/earth, hence none of the brushes are earthed. Earlier models used the Type B regulator which switches the power from the ignition to the field winding and the other end of the winding goes straight to earth via the earthed brush terminal. I am not sure when the cut off date happened but you may have the Type B regulator, so be careful when buying.

    Deviation: I did get out on the bike for 20 mins to test retarding the timing but I set it too far so have advanced it a bit more and will retest tomorrow. Certainly the retarding does make for a more comfortable ride but it makes starting difficult if you go too far. Also increases the risk of a heavy kick back. I did manage to solve the backfire when throttle is off going downhill, had to increase one mixture screw and it now matches the other.


  10. peanut

    peanut XS650 enthusiast & inveterate tinkerer Top Contributor

    the reg rectifier I suggested is only £11 ;) this one will do you fine.
    Earlier I saw a connector kit you can crimp or solder to the regulator for about £1. 90 so the whole thing cost only £14.00 !
    similar to the one in this link
    can't see how you can make your own for that sort of money.
    Paul Sutton likes this.
  11. Paul Sutton

    Paul Sutton Sprained Ankle Top Contributor

    Peanut, that is incredible! There is no way I could match that price. I will have a look for the bike schematics tomorrow or Monday to determine if they are type A or B.
    Thank you very much - This will keep me busy!
  12. retiredgentleman

    retiredgentleman XS650 Guru Top Contributor

    There's no need for a zener diode or a MOV, if you are using the stock type of alternator on these bikes. If you have a regulator that is working correctly, the voltage will stay between 14 and 14.5 volts while driving down the road. Of course, at idle the voltage drops down to approximately 13 volts.
    peanut and Paul Sutton like this.
  13. Paul Sutton

    Paul Sutton Sprained Ankle Top Contributor

    I have been studying the XS SH wiring diagram. There are two power circuits:
    • Red Wire: Always live and connects directly to the battery positive and feeds ignition switch.
    • Brown Wire: Only live when ignition is switched on.
    I am not clear on the following at the rectifier/regulator connector:
    • Red seems to be the line where the output from the rectifier goes directly to the battery for charging. I assume the Red is also the voltage reference line used by the regulator.
    • Brown: What is this? Does it just supply ignition switched power to the stock regulator circuitry?
    If I make a DIY rectifier/regulator using the Lucas 14Tr regulator in #6 above then the voltage sense line should really go to the Red Wire to be as close to the battery voltage as possible. If I do this then there will always be power to the Lucas 14Tr regulator even with ignition off.

    If I connect the regulator voltage sense line to the Brown Wire then it is only powered up when ignition is on - But I may not be sensing the true battery voltage due to drops in the Brown Wire because of the several connectors in that line, or do I need to clean up all the connectors to ensure the Brown voltage equals the Red voltage?

    Can anyone advise me on the tried and true practical solution of where to connect the voltage sense wire - Red or Brown?

    Thank you very much.
  14. retiredgentleman

    retiredgentleman XS650 Guru Top Contributor

    Paul; With all of the cars, trucks and motorcycles that I have driven over the last 54 years, the voltage regulator always senses the voltage on the brown wire, which is the voltage downstream of the ignition switch. Don't be concerned that the regulator is not sensing battery voltage on the red wire. The brown wire is indirectly sensing the battery/alternator voltage, its just doing it on the load side of the ignition switch. Yes, we do not want to have power to the regulator all the time such as with the key off.

    Yes its important to have a low resistance path from the battery to the brown wire. So, you want to have the ignition switch and the main 20 amp fuse, both clean and shiney. If the main fuse is an old glass fuse type, then get rid of it and replace with a new automotive blade type. The ignition switch can and should be taken apart, and the contacts cleaned up with some fine emery paper.
  15. Paul Sutton

    Paul Sutton Sprained Ankle Top Contributor

    Thank you retiredgentleman, you have put me on the right path now. I placed an order for all the components earlier today. I paid more money to get a better quality 3 phase bridge from International Rectifier. The completed full price including heat shrink, cable and an 8 pin socket will be about £30. A new Chinese unit is about £66.

    Thank you.
  16. Paul Sutton

    Paul Sutton Sprained Ankle Top Contributor

    Help Please : I have received all the components and completed all the hardware construction and wiring except for the regulator. I purchased a Cargo 130642 Type A regulator and this has 4 wiring points:
    • Black Wire = D-
    • Yellow Wire = D+
    • Metal Casing = DF
    • Red Wire = B+
    Note: These assignments above coming from the manufacturer must be correct? It just seems strange that the metal casing DF is the control for the field winding and not to be earthed.

    I will be very grateful if anyone can enlighten me on the DF wiring - Thank you.
    Last edited: Jul 19, 2017
  17. Paul Sutton

    Paul Sutton Sprained Ankle Top Contributor

    After 2+ hours searching through various circuit diagrams and conversion tables I come to the following conclusion regarding the Cargo 130642 (Lucas 14Tr replacement):

    Black Wire D- is the battery negative to ground.
    Yellow Wire D+ is the indicator wire and should be tied to positive (ignition on brown wire)
    Metal Case DF is to the field winding (green wire to rotor)
    Red Wire B+ is the battery positive (ignition on brown wire)

    It seems the Cargo 130642 (Lucas 14Tr replacement) metal case must be isolated from ground.

    Does this all seem reasonable????

    Note: The following PDF shows the different pin nomenclature and pin layouts for several regulator manufacturers:
  18. DoubleE

    DoubleE XS650 Addict

    Recheck your "Red Wire B+". It is likely this should come straight from the battery and fuse (should be all red wires), and not through the "ignition on brown wire".
  19. Paul Sutton

    Paul Sutton Sprained Ankle Top Contributor

    Thank you DoubleE. The theory states that Red B+ should go directly to the Battery so that the voltage it senses is the true charging voltage. However, on the XS this would leave the power permanently switched on to the regulator which may not be a good idea? By using the Brown wire via the ignition switch and harness I have a 0.3 Volt drop at present which will push the charging voltage up to about 14.7 Volts. This should not be an issue but I plan to minimise the voltage drop further by either adding a small relay between the battery and regulator or thoroughly clean the ignition contacts as suggested by "retiredgentleman" above.

    Do the other assignments seem correct to you? It just seems strange to me that the regulator case goes to the field winding and the Black goes to ground. I would have expected the opposite.

    Thank you.
    Last edited: Feb 5, 2017

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