Reg/Rec replacement, did I get the right one?

[Fang]

Went out to the local swap meet today
Found this Reg/Rec
I've got a 1979 xs650
Would this work?
No labels or names on it
Only thing I can see are the 3 dimple looking things between the fins close to the wires
Looks like
3 yellow
1 red
1 green
1 black

 

[TwoManyXS1Bs]

Yeah, those things freak me out.

It's like getting a letter marked:
"You could be a winner! Details inside! (offer void if envelope is opened)".

With a generic heatsink/housing and no markings, it could just as well be a coffee warmer.

To be a type suitable for the 70-79 alternators, I'd expect an additional wire, which would connect to switched power (brown), to turn the thing 'on'.

Suppose we assume that:
3 yellow - 3 stator wires
1 red - battery(+)
1 black - battery(-) (ground)

Then, test those 5 lines just as you would if testing a rectifier.
If those 5 lines pass the rectifier test, then:

Connect red to battery(+)
Connect black to battery(-)
Measure voltage between battery(+) and green.
If any voltage shows, then it may be the 80-83 type.
Or, it could be a PMA rec/reg...

 

[XSLeo]

Being it has three yellow wires it's probably for a PMA, Yamaha used three white wires.
Leo

 

[Scallywag303]

Looks like a 3 phase reg/rec as XSLeo said for a pma. Pretty universal, a lot of scooters use them.

 

[Fang]

To be a type suitable for the 70-79 alternators, I'd expect an additional wire, which would connect to switched power (brown), to turn the thing 'on'.

Suppose we assume that:
3 yellow - 3 stator wires
1 red - battery(+)
1 black - battery(-) (ground)

Then, test those 5 lines just as you would if testing a rectifier.
If those 5 lines pass the rectifier test, then:

Connect red to battery(+)
Connect black to battery(-)
Measure voltage between battery(+) and green.
If any voltage shows, then it may be the 80-83 type.
Or, it could be a PMA rec/reg...

If it is the one for the Pma kit would it do any harm to install it on my bike without the pma set up?
I'd like to get the pma someday but funds are tight right now, just trying to clean up the electronic components for now and it would be nice to combine the reg/rec
And if it is the 80-83 type would I be able to modify it for my 79?

 

[TwoManyXS1Bs]

Based on the results of your tests, I'm still convinced that it's a coffee warmer.

This is the kind of rec/reg that'll work on your 70-79 alternator:

http://www.mikesxs.net/parts/yamaha-xs650-solid-state-rectifier-regulator-70-79

 

[XSLeo]

A bit of info on reg/rec's,
A PMA or Permanent Magnet Alternator set up uses a rotor with permanent magnets mounted in it. As these magnets spin around the stator, this induces an AC current flow in the stator. This AC current flow comes out of the stator on the three wires. At the reg/rec there is a set of diodes the convert This AC current to DC.
The regulator once this current flow reaches 14 volts or so just shunts this voltage to ground.
The stock system uses a FEA, or Field Excited Alternator. This set uses a field coil in the rotor. The reg controls the current flow through the rotor. On your 79, it uses a separate reg and rec. When you turn on the key the reg reads the voltage on the brown wire. If it is below the preset of about 14.5 volts, it sends current out on the green wire to the rotor. This AC current flows through the rotor. This magnetizes the rotor. As the rotor spins it induces an AC current in the stator, This AC current flows out on the three wires to the rectifier, where it gets converted to DC and sent to the rest of the bike.
Now when this DC voltage reaches the preset of about 14.5 volts the regulator turns off the current flow through the rotor, this stops the magnetism and stator output.
On the 80 bikes that use the combo reg/rec, it operates about the same as the separate set up but when it reads a low voltage it doesn't send current to the rotor, it controls the ground of the rotor. The brown wire sends current to the rotor, the green wire from the rotor goes to the reg/rec where the reg turns on/off the ground.
The after market makes two types of reg/recs, on is designed to work the same as the 70-79 regs and recs, A plug and play set up.
They make one that works like an 80 up that is plug and play for them.
To use the 80 up type of reg/rec on a 70-79 bikes is not a plug and play, it needs the brushes rewired and the grounded brush isolated from ground, thus the three nylon screw mod. A quick search for the three screw mod while find all the details you need.
There is a way to use a PMA type reg/rec on a FEA, You hook it to three wires on the stator output. Then you have to hotwire the rotor so it has current flow when the key is on. This causes the alternator to create it's max output at all times just as a PMA stator does. This lets the PMA reg/rec shunt output to ground to control voltage.
Not a very good way but it can work.
Leo