Author Topic: A quick how to on switching to solid state regulator / rectifier  (Read 22688 times)

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devbear12

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Ok so i had a delema that took some time to figure out.  I have a completely stripped 750 with old school electronics that i couldnt hide due to no room>>>>  If you have this problem i might have a solution for you.  The alternator used on the sohc 750's is the same exact unit as used on any dohc750 and dohc900.  The only differance is that all of the dohc bikes have a solid state regulator rectifier that is relatively small (tiny compared to the sohc bikes) and isnt ugly (unlike the hidious sohc bikes unit).  so here is how to hook it up with or without factory wiring.  Oh by the way i found one of these units at a local salvage yard for under 40 bucks. :)  Please note the connectors i am talking about is for the solid state unit off a dohc bike.  Also please note: there are two black wires on the new regulator assy. the wire hooked to the larger connector is to be attached to the alternator, if you are using a unit that does not have connectors there are two rows of wires coming out the end.  the row with the yellow wires will all connect to the alternator, the shorter row will all hook to the bike side.

If you are using factory wires then match colors as following

large connector (on rectifier)
white wire from old rectifier to alternator - cut out old rectifier and wire to white wire on new
green wire from old rectifier to alternator -"                              " wire to black wire on new
Yellow wires from "                           " - "                              " wire to yellow wires on new

Small connector
red/white wire - wire to red white wire on old regulator
black wire - wire to black wire on old regulator
green wire - wire to green wire on regulator

note: the green wire from rectifier can either be cut and left alone or can be spliced into the new green wire on the reg/rec.  Its just a chassis ground no damage will be caused by cutting and leaving.

With custom wiring
Large connector (on rectifier)
white wire on rectifier - white wire on alternator
black wire on rectifier - dark green wire on alternator
three yellow wires on rectifier - three yellow wires on alternator
       note: it doesnt matter which yellow wire goes to which (connect individually though)

Small connector (on regulator)
Black wire on regulator - ignition (batt +):brown wire on ignition switch (not brown/white)
Green wire on regulator - Chassis Ground
Red/white wire on regulator - batt + with inline fuse (30amps)

hope this is helpfull to someone, i think it is new posted info, i surely just found out the hard way.
« Last Edit: March 17, 2009, 07:53:42 pm by devbear12 »

Offline Skunkmiester

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #1 on: August 04, 2009, 01:18:01 pm »
Hmm, strange.

My aftermarket Reg / Rec has a different line up and so does my bikes wiring.

It is as follows.

Bike side of  Rectifier block:
3 Yellow > alternator
Green > Earth
Red/White > Fused red wire

Aftermarket Rectifier block:
3 Yellow > would connect to 3 yellow on bike side
Black > would connect to Green on bike side
White > would conect to Red/White on bike side



Bike side of Regulator
Green > Earth
Black > Earth
White > Alternator White

Aftermarket has
Green
Black
Red/White


So if I was to follow your wiring, I would need to swap the red and white from the Rectifier block, over to the regulator block. And use the white lose wire (that would have gone into the Regulator) and pipe it into the Rectifier block.

Is this correct or will I start to smell smoke :)

Thank you in advance.

In a sealed unit, should the regulator or the rectifier be hooked up to the battery via the fused red, surely it is the Rectifier.
1973 CB 750 Cafe Racer
1992 (original) Fireblade

Offline Skunkmiester

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #2 on: August 17, 2009, 10:38:14 am »
As the white on the white on the Regulator and the Red \ White on the rectifier are connected (tested with multimeter) does that mean that it will not matter?
1973 CB 750 Cafe Racer
1992 (original) Fireblade

Offline C.Doyle

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #3 on: December 07, 2009, 11:20:15 am »
It would be great to see a FAQ sheet about wiring up solid state regulator / rectifier's from diff. models as it seems allot of people including me are having trouble. Mine's from parts'n more and the wiring diagram if you would call it that, was totall crap.



wired up right now is

 BIKE TO RAGULATOR unit

black-white wire with red line
green-green
white-black

BIKE TO RECTIFIER unit

yellows-yellows
green-black
red with white stripe-white

this so far was the only way it didn't melt wires, short fuses, or turn ignition on... cb750 k5


Offline dave500

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #4 on: December 13, 2009, 12:31:36 am »
i was using a solid state rec/reg from a vf400,these bikes have a permanent magnet field,the regulator dumps the excess to earth,i ran a multimeter taped to the headlight for a few days and it did get pretty high under revs,like 15 plus!!i used that for 2 years and now have one from a 900,the voltage is more stable,i now have a vdo 50mm voltage meter secured neatly between the guages,idleing the voltage will drop below 12,itll sometimes approach 15 riding(i always use the headlight),i feel its a better unit.

Offline C.Doyle

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #5 on: January 29, 2010, 01:58:57 pm »
Has anyone els had this problem? Bump

Offline BrianAdair

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #6 on: January 29, 2011, 02:35:32 pm »
Anyone had good results with this??

I'm not, I have a DOHC reg/rec and wired it up with the pics I found here on the forum, and I'm getting over voltage.
It will rise to 17volts at 3000rpm and burning out my LED lights.

This is what I went by.



Please help.....?! ;)
If I hook all the old SOHC components back up it only rises to 15 volts.

Offline TwoTired

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #7 on: January 29, 2011, 03:07:21 pm »
Do you have schematic of the parent bike showing how it was connected in its original form?

Or, a schematic of the inside of the DOHC R/R. 

Do you know if the one you have is still undamaged by experimental wiring?
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline BrianAdair

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #8 on: January 29, 2011, 05:23:16 pm »
No, but I might be able to go back and look at the harness at the wrecking yard.

No, I was wondering the same if one was available.

And....no, :-[  I did have a friend bring another R/R which is the same as the DOHC off of his CB650 and it done the same.
I tested for resistance on all wires the only ones that have any are the black ones, one is on the Regulator, and the other on the Rectifier.

The DOHC R/R has the same color code wires as the picture above.

Offline TwoTired

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #9 on: January 29, 2011, 05:45:38 pm »
Do you know he make and model of the bike on which it was found.

Do you have a multimeter with a diode test function?
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline BrianAdair

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #10 on: January 29, 2011, 06:17:40 pm »
Do you know he make and model of the bike on which it was found.

Do you have a multimeter with a diode test function?

It was a DOHC cb750, not sure of year thinking around 79 or 80.

I have a fluke digital meter. it has AC/DC Volts, amps, ohms.

Offline TwoTired

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #11 on: January 29, 2011, 06:52:02 pm »
Flukes usually have a diode test function, often on or within the ohms selection.
Look for a symbol like -<|-

Use it to check black to black both probe polarities.

Then check each black to wht in the same way.  All disconnected from bike.  You are checking the unit independently.

If everything reads low/zero ohms, the Reg is probably toast/shorted internally.  They don't like miswires very much and complain by dying.
If you get other interesting readings post them.

If there are two black wires how did you select which when the ign and/or alternator.

Cheers,
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline BrianAdair

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #12 on: January 29, 2011, 07:27:08 pm »
My meter wouldn't work it doesn't have the diode setting.

The only one i can get anything on is the 2 black wires.

The way i chose which set of wires was the way it was originally on the DOHC, large plug with the 3 Yellow, White, and Black.
Then the smaller plug, White/Red stripe, Green, black.

Offline TwoTired

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #13 on: January 29, 2011, 07:34:22 pm »
Do either of the white and black wires to alternator have continuity to the green wire?

Have you measured the Black ignition wire for voltage while running?  Does it match the battery voltage?

Which Fluke model do you have?
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline BrianAdair

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #14 on: January 29, 2011, 07:59:45 pm »
Do either of the white and black wires to alternator have continuity to the green wire?

Have you measured the Black ignition wire for voltage while running?  Does it match the battery voltage?

Which Fluke model do you have?

Yes, the black ignition wire does, which for some reason all my power wires do, its only 2 ohms I eliminated it down to the kill switch, if i disconnect it, then it doesn't. I assumed that it was from the coils, this is with the bike not running.

The white to the field coil does also with the green on the field coil.

Yes I have and it rises just as the battery does, that's why my LED indicator light blew out I'm assuming.

It's a Fluke T5-600. 

Offline TwoTired

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #15 on: January 30, 2011, 12:51:58 am »
Do either of the white and black wires to alternator have continuity to the green wire?  (With the Reg disconnected from the bike.)

I just looked up your meter specs.  It's not going to be useful for examining/checking electronic devices without a diode test function.

Silicon devices need a minimum voltage to activate.  With insufficient voltage they simply won't turn on.  So, you can't tell if they are working or not with the two polarity tests I asked about.

Anyway, I was trying to get enough info to access whether your regulator is in a working state.  I don't have confidence it can be done with your meter.

Without a known good regulator, it would be luck to sort out wiring, without knowing the circuit that it works in, or the circuit inside it.

I can't help without some kind of foundational knowledge.  Sorry.



Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline BrianAdair

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #16 on: January 30, 2011, 08:12:58 am »
Do either of the white and black wires to alternator have continuity to the green wire?  (With the Reg disconnected from the bike.)

No, they don't.

I just looked up your meter specs.  It's not going to be useful for examining/checking electronic devices without a diode test function.
Silicon devices need a minimum voltage to activate.  With insufficient voltage they simply won't turn on.  So, you can't tell if they are working or not with the two polarity tests I asked about.

I will see if I can get another meter, or barrow one that will test diodes.


Offline BrianAdair

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #17 on: January 30, 2011, 02:36:30 pm »
Ok, i have a meter with a diode setting now.


small plug on the R/R has White/Red stipe wire, Green Wire, and Black wire.

Black wire, with red probe on it, to Green wire, I get .879. reverse the probes and I get .967

White/red wire with Red probe on it, to green wire I get .OL reverse the probes and I get .811


Large plug, 3 Yellows, White and Black wires.

Red probe on Black wire to White wire, I get .845 reverse the probes I get .894


Now jumping across the plugs,
Red probe on Black wire on the large plug to the Green wire on the small plug I get .879 reverse the probes I get .962
0 on Black to Black either probe.
Red probe on White wire on large plug to Green on small plug i get, .oL reverse probes I get .476

Red probe on white wire on large plug to Black wire on small plug I get .780 reverse probes I get .844


Offline TwoTired

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #18 on: January 30, 2011, 06:25:43 pm »
I can't say for sure.  But I would be unhappy with those readings and suspect a fudged regulator.

To verify, run the bike with your connections, and measure the voltage across the White and green connections to the alternator.
When the battery is in need of power, all the voltage delivered to the regulator on the black wire (small plug) should be passed to the White wire on the alternator (IOW, voltage measured across the White and green wires).

When the battery voltage rises above 14.5V, the Alternator white to green voltage potential should be reduced (telling the alternator to back off).

If your connections are wrong or the regulator is shorted, as your measurements seem to indicate, then the alternator will put out full power regardless of battery voltage.  (Remember, the alternator output varies with RPM, too, and the battery must be full to attain an over voltage condition.)

The stock regulator only controlled the power feeding the White alternator wire and expected the Green to be always connected to the frame or battery NEG.    Since I don't know the internal connections of your regulator, I don't know if the white or black wires have an internal connection to the Green (small Connector) or if trying one of those wires to frame ground overloads the internal circuits to failure.  While it can be designed to tolerate miswires/unexpected connections to the wrong thing, such circuits are usually more expensive, and not always employed into controlled environments as the stock bike//application would be.

Clear enough?
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline BrianAdair

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #19 on: January 30, 2011, 06:48:28 pm »
The stock regulator only controlled the power feeding the White alternator wire and expected the Green to be always connected to the frame or battery NEG.    Since I don't know the internal connections of your regulator, I don't know if the white or black wires have an internal connection to the Green (small Connector) or if trying one of those wires to frame ground overloads the internal circuits to failure.  While it can be designed to tolerate miswires/unexpected connections to the wrong thing, such circuits are usually more expensive, and not always employed into controlled environments as the stock bike//application would be.

That's what I came up with also, wanting to see inside the thing to know how it kills the alternator.
I understand how the old stuff worked.

I don't think the regulator is good, the way I had it wired has to be the only way it could hook up without shorting out and blowing fuses. It's not shutting the alternator off, or regulating the voltage, I had around 18volts @3k RPM.
Now at Idle it has 12 volts but rises as the RPM does and doesn't seem to stop rising.

Offline harald

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #20 on: October 12, 2013, 11:45:56 am »
 You have to run a seperate wire that connects the green from the Alt. to the white on the reg/rectifier unit. Apparently the oem green wire  on the sohc connects to all the other grounds. The dohc unit needs to see this wire directly (dont ask me why), so run a straight wire  to it.  (Above text is copied from an older post) :-*


The dohc reg varies the connection to ground to control the field current, while the SOHC reg varies the connection to 12V that is why coil field ground (green wire must go striaght to the white wire on the dohc reg)




« Last Edit: October 18, 2013, 08:46:57 am by harald »

Offline ianlou

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Re: A quick how to on switching to solid state regulator / rectifier
« Reply #21 on: July 27, 2017, 01:58:50 am »
I actually have an old reg/rec from an '86 honda vt700, anyone Know if thats the same one? I cant imagine any reason it wouldnt be