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  1. #1

    Inside an LR21 polaris rectifier & circuit diagram

    Got a bit bored at work so took apart my rectifier regulator module, this is the unit after I stripped it, cleaned it out and identified the components.




  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Cool. I have been meaning to document the insides of these things, just never got around to it.

    What was involved in opening the case and removing the potting materials?

  3. #3
    I cut away the plastic case and then put it in boiling water to soften up the material inside and it made it fairly easy to peel away.
    I did desolder every component after I drew out their locations.. then cleaned each one up and the pcb then resoldered them all back in.

  4. #4
    I have now dismantled an LR23-1 if its any interest posting the similar info..

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    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Mark-UK View Post
    I have now dismantled an LR23-1
    if its any interest posting the similar info..
    Yes please!

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    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Mark-UK View Post
    Got a bit bored at work so took apart my rectifier regulator module, this is the unit after I stripped it, cleaned it out and identified the components.


    Are you sure about the Zener voltage?

    11.9 volts seems a bit low, I was expecting something closer to 13 volts, maybe a bit higher. I don't think there is any quiescent current draw from the battery through the LR module on Red/Purple when the engine is shut down.

    Is the SCR part number 1989, any other identifying marks?

  7. #7
    Yes that was definitely the value of that zener, but remember it is connected to a transistor which will add another 0.5 volts across its internal diode. The SCR device i did find some info on, i have the other LR23 here as well im just looking at it..
    the only other identifying mark on it is a Motorola logo and 9327 after it. but thats not usually part of the part number.

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Mark-UK View Post
    Yes that was definitely the value of that zener, but remember it is connected to a transistor which will add another 0.5 volts across its internal diode...
    I was thinking of the series resistors and the zener alone, but I suppose the less than 1 milliamp parasitic flow through the resistance isn't going to bother the battery much.

  9. #9

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    i think i caught a mistake, on the drawing (second image from Mark-UK), a854 b->c and c->b right ?
    i tried hard ( i really did ) to make a simulation work like in the picture and only with b c reversed it did (also seem to mach my LR23)

    i also opened my lr23. mine was really hard to clean that silicone it was molded in. after i finished i left a piece of that material in thinner overnight and it really broke its strength, to late for me but maybe will help someone, although i do not know what effect would have on other electronic components and board.

    here are some photos of my lr23 board and oscilloscope ..:



    i destroyed irfiz24g legs when cleaning that thing..




    regulator connected, not sure it was working correctly, measurement between yellow and r/pur stator wires


    regulator connected, not sure it was working correctly, measurement between black wire/gnd/0V and +12V (same R/PUR wire, voltage more like /14..16..V and rising with time and rpm)


    measurement taken without regulator connected between yellow and r/pur stator wires
    20Vdivision->60V peak, 2ms time division->4ms cycle length


    4761rpm, 100V peak, measurement between stator wires (yellow - R/PUR)


    regulator connected, not sure it was working correctly, measurement between yellow and r/pur stator wires


    4347rpm, 100V peak, measurement between stator wires (yellow - R/PUR)

    *descriptions are under corresponding pictures
    *if hz is displayed multiply by 10 to find rpm
    *when AC value is shown it is RMS
    *R/PUR = red purple wire as in electric schematic
    *regulator not connected unless specified (if sine is complete then regulator was not connected)

    this is the simulation i built (only for the rectifier/regulator part, right part of board with fet seem to be just for conditioning when motor running):

    http://www.falstad.com/circuit/circu...125+1+2+3+3%0A

    parts on the right, 10uF capacitor and 1k resistor simulate the battery
    now, if my understanding is correct, then this circuit allow over 100V (at high rpm) tu be pulsed directly (not on every cycle, but still) on battery (and mfd). well this could explain why the 18V zener i installed in mfd as replacement for the unknown smd part would burn the fuse.

    this could also be the reason for the fast aging of the original protection diodes in mfd.
    all this theory is only true if my lr23 is not out of specs actually, thing which i still investigate as it seem to overcharge (>15V in original form, now with all semiconductors replaced: scr, transistors, zener (mine seem to be 11V) even fet , even >16V, and on osciloscope now it seem to allow all pulses, i didn't oscilloscoped it in the beginning)

    if this design is so bad then i am thinking to build a simple fet regulator, there seem to be available irf840 n-fet 500V 8A, for ~ 1$. this
    should give steady 14.2V.

    http://www.falstad.com/circuit/circu....025+2+1+40%0A

    parts on the right, 20 resistor and 100uF simulate the battery (load)


    and a question, i accidentally touched the yellow wire from stator to electrical box case (ground) for ~1 second (maximum 2s), the other side R/PUR is connected to battery +12V.
    i tested it afterwards and electrically it seem ok (ohms and voltage generated with motor running), but i wanted to ask if this could damage it and how long would it take for it. i have an 40A Pb battery.

    thnx and btw i finally tested my sl750 on water a week ago and it seem to run very good :] after a long repair and many years of waiting to be repaired.
    i learned enormous with this. thank you! to this forum and to its very helpful users!
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  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Thanks for posting more info!

    None of the scope images have the vertical scale and zero line visible, so I cannot be sure what voltages are being shown at different parts of the waveform. Most particularly the Black to Red/Purple DC trace.



    I suspect that the rectifier is working but the regulator aspect is not, hence the increasing 'battery charging' voltage with increased RPM.

    Can you post your 'correct' schematic for the LR module?

    Your simulation may not match the actual circuit operation. The regulator and rectifier work by controlling the current through the Yellow wire from the stator coil. Battery charge current flows into the battery when the regulator Yellow wire is switched to ground and the Yellow stator wire was at that instant producing a strong negative voltage.

    'Lifting' the stator Yellow wire to ground level forces the battery end of the charge coil (Red/Purple from the stator) to inject charge current into the battery. That charge current in turn raises the voltage across the battery and the LR module's regulator sense voltage on Red/Purple.
    Last edited by K447; 05-21-2017 at 09:51 PM.

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