Topic: TwoTired!!!!!!!

[Dusthawk]

Does this look right to you? The reg/rec combo unit I have is from an 80's honda. Will it work as shown for my '71? I have three different wiring diagrams, but don't know if I interpreted correctly.

Jeff

[SD750F]

Jeff,

I am a little confused why you have two black wires? To have one attached to your ignition power line, and the other attached to ground is cause for concern. The Regulator/Rectifier that I bought has only one black wire... Mine didn't have the bundles or wire sets together like they were on the standard CB750 wiring diagram but made sense after you consider change. My old regulator has three wires, Black (Bk), Green (G), and White (W) in one bundle, and 3 Yellow (Y), Green (G), and Red/White (R/W) on the rectifier.

The instructions I got with my set read:

Remove left hand plastic side cover. Locate & remove the regulator and rectifier. From the replacement rectifier/regulator, identify the 6 gang wire bundle (my addition here, actually a 6 pin connector with 5 wire). Connect the black ire to the black wire that plugged into the regulator. Connect the red, green, and 3 yellow wires to the corresponding colors that plugged into the rectifier. Solder and heat shrink all connections.

My other concern that was brought up in another discussion was that the DOHC used a "Low Side" or sinking regulator for the field coil. And the SOHC used a "High Side" or sourcing regulator. Maybe they can be used in each if the polarity is maintained but that is unknown unless you know the real circuit design...

I have attached a photo of the combination unit I purchased on eBay... And Once I find a good source of aluminum heat sink/enclosure I like, maybe I will make a direct SOHC replacement using the newest technology for all the members here...

Scott

[oldfart]

Does this look right to you? The reg/rec combo unit I have is from an 80's honda. Will it work as shown for my '71? I have three different wiring diagrams, but don't know if I interpreted correctly.

Jeff

Black NEVER goes to ground on a Honda.  The reason there are two black wires is because one is the battery sense wire, that signals the regulator.  The other black wire goes to the field coil.  Look for my previous post for drawings comparing DOHC and SOHC regulators.

[TwoTired]

Hi Dusty,
For the most part what you labeled looks correct to me EXCEPT the white and black wires at the top of your diagram.  Since you have grouped them with the yellows, might I assume they are bundled for an alternator destination?
If this is so, then it seems reasonable to assume the white and Black wires attach to your alternator's field coil.
I do note that the CB650 wire diagram shows both a white and Black wire going to the alternator field connections.  Which supports the assumption.
If that upper black wire in your diagram does not bundle with the yellows, then perhaps it is a sense line???  I don't know.  But, I don't think I would ground it if the unit truly came off a Honda.  Black means hot not cold like a ground.

So, I think it should connect to the alternator field.  (feel free to refute the logic I've applied)
This is where the wicket gets a bit sticky.
The CB750 field coil wires are White and Green and the green wires are Grounded.  But, I don't know exactly where they are grounded in the cb750.

Were I there, I would measure the green wire (unconnected to the bike) exiting the alternator case, for resistance to the engine case.  If found to not be grounded to the engine case internally, then it probably won't matter which polarity you connect the Black and White wires from the Regulator to the White and Green wires of the alternator.

However, if the 750 alt field  Green IS connected to the engine case, then I would be wary of connecting a Black= +12V Honda convention to the Green wire where Green = 12V neg battery connection.
Originally the CB750  Field coil was powered from the White wire where, up to +12V was applied.

Could be, that your new regulator reversed the the role of the white wire so it is a return line instead of a power line.  But, that doesn't necessarily mean it can be grounded.

This is getting pretty wordy.  So, I think I will stop here and wait for information about your field coil grounding.  If it isn't grounded, we won't have to do electrical testing of the wires to determine safe connection for both alternator and regulator.  If it is grounded, I'll type instructions to safely determine wire functions and what the internal design of the Vreg can tolerate.

Cheers,

[Dusthawk]

I realize now I should have done this last night but I was tired and posted this after trying to figure it out on my own. Wiring schematics have never been a strong suit of mine. Here is a pic of the unit I have. As you can see, there are two groups of wires exiting the unit, on top five wires, white, 3 yellow, and a black. On the bottom, there is the red/white stripe, green, and black.

I'll be moving Rita up here within a week or two, so I'll be able to check the continuity as you suggest. Otherwise, I hope I didn't just waste $30.00

Jeff

[Dusthawk]

Also, if it helps any, this is the diagram I was trying to work this out last night with. Coming out of the regulator on the bottom right are three wires, two labeled white and black, but the third going to ground, isn't color labeled. Out of the regulator is a green instead of a black, and is going to ground. Here is my confusion.

[Bodi]

Every SOHC4 induced field alternator I've worked on has had an isolated field coil, neither field coil wire is grounded. The coil wires are presumably colored because what they connect to - in the standard system - is ground (green) and the field power from the regulator (white).
This new reg/rect unit powers the field coil slightly differently - one field coil wire is battery power (a black wire on Honda systems, the field coil one is probably jumpered internally from the other black wire) and the other is the regulator controlled white wire. With this unit the white wire is close to ground (zero volts) when the regulator is asking for maximum alternator output - battery voltage below 13 volts or so - and closer to battery voltage when it's asking for minimum alternator power - battery voltage above 14 volts or so. The end result is the same, the field coil voltage varies from roughly battery voltage to a low voltage.
It shouldn't matter which regulator wire - black or white - goes to which coil wire - green or white. The magnetic field from the field coil is formed with the N and S poles along the crankshaft. The rotor pole pieces bend this field so that alternating magnetic poles are pointing out around its circumfrence. Since the rotor and pole pieces rotate, these poles sweep across the output coil windings making the electricity. It doesn't matter which pole is which at the coil, either way will still end up as alternating N and S poles around the rotor. So you can either connect white to white and have one connection match, or connect black to white and avoid the alarming sight of a green wire connecting to a black wire - on a "normal" Honda wiring harness that would be a major no-no!