Topic: Question on voltage reg.....

[brcree]

Has anyone up graded the stock voltage reg. on a 76 cb 750 to a more modern unit?

[HondaMan]

Some have, but they get mixed reviews. Avoid the ones that tout "increased alternator output" as they are sometimes shunt-type units, which will toast the alternator windings after a while. The 750 has a robust system as-is: if yours is having issues then we should talk about the broken thingie it is now harboring. 

[brcree]

Thanks for the reply Honda man...as i try and remember correctly...when you turn the key to on you should get a magnetic pull from the stater...using a screw driver....correct?

[strynboen]

no the rotor gets mag..from the coil behind the rotor.

[Bodi]

"when you turn the key to on you should get a magnetic pull from the stater...using a screw driver"
In a way. What we generally call the "stator" is the three-phase output coil assembly mounted to the alternator cover. This alternator type, "induced field", uses an electromagnet to produce the magnetic field that makes the electricity. This electromagnet "field" coil is the inner coil assembly on the alternator cover. The rotor has various iron pole pieces in an aluminum casting, the iron bits bend the magnetic field from the field coil so it sweeps over the stator coil wires when the rotor turns.
The regulator turns the field coil power on and off depending on the electrical system voltage. "Upgrading" to an electronic field controlling regulator can not make more power and, as HM says, some new regulators work differently - they power the field coil all the time and control the output by wasting the extra power. This wastes engine horsepower and can cause burnt connections in a tired wiring harness.
With the key on you might feel some magnetic pull on a screwdriver if you hold it near the alternator cover. This is from the field coil though, not the stator.

[brcree]

Thanks guys...just tried the screwdriver on the part you suggested with key on....no magnetic pull at all........

[TwoTired]

Try using a thin feeler gauge blade.

[magnum56]

Thanks guys...just tried the screwdriver on the part you suggested with key on....no magnetic pull at all........

He said you "MIGHT" be able to sense the magnetic pull from outside the Alt cover. 
Please do not consider "not" feeling the pull as a definite problem.

If you don't have one already, I would recomend investing in a "multi-meter" and review the maintence manuals for various test procedures there.

And always make sure you are preforming your tests with a fully charged battery.
   

[brcree]

I have the cover removed from the eng...........and will try the feeler guage. I'm using a meter as well....and know how to use one.

[TwoTired]

The field coil is an electromagnet.  When it is provided with 12 V, it makes a magnetic field.  The poles are (mostly) directed radially.

[brcree]

We are talking about the silver doughnut shapped unit in the middle of the cover ..correct? I used a small piece of wire...not copper....and still nothing.....The batt,. is at full charge.

[TwoTired]

Can you measure the resistance of the field coil?

[magnum56]

We are talking about the silver doughnut shapped unit in the middle of the cover ..correct? I used a small piece of wire...not copper....and still nothing.....The batt,. is at full charge.

Yes the "dough nut" is the field coil.  It has to be "activated" by the regulator to produce the magnetic field.
As TwoTired has indicated, check the resitance of the field coil with the multi meter.
 
   

[brcree]

OK Mag...did the test no resis..   also did a volt check across the g,w,and black wires on the reg.....g to w 0....g to b 9.5  with key on

[TwoTired]

Measure the field coil resistance disconnected from the bike.  S/B 6.8 Ω.

Zero resistance is a direct short.  infinity is usually and open circuit.  Meter leads have resistance, too.

[brcree]

Placed meter leads across both wires and got 0.01 reading.

[TwoTired]

If your report is accurate, then the field coil is shorted.

What meter scale are you using?
What does you meter's manual say is the display indication for opens or shorts?
What does the meter read with the probes touching and apart?

Cheers,

[brcree]

1. I have the meter setting  at 20 DCV.....2. If a reading....its good....with just o in window ..or Infin....short.  3. 0.05.

[KRONUS0100]

i have a new solid state voltage regulator, and a rectifier from Tony at OREGON MOTORCYCLE PARTS.  they look like the stock pieces and they work great.

[brcree]

Kron...whats your price?...I thought about taking this rout.

[TwoTired]

1. I have the meter setting  at 20 DCV.....2. If a reading....its good....with just o in window ..or Infin....short.  3. 0.05.

Multimeters are labeled as such because they have multiple functions depending on the selector/scale used.

In basic DC cicuits there are three primary properties to be concern with:  Resistance (R), Voltage (E, for Electromotive force), and Current (I).  They behave in this relationship.  E=I x R or the equation variations of I=E/R and R=I/E depending on which value you wish to derive from the other two properties.  A multimeter can measure each of these if it is set up in the correct way.

You will not be able to measure resistance (Ω, or ohms) directly on a meter set up to read voltage (DCV, Direct Current Voltage)
You must set the meter to the lowest ohms scale (in order to read within that expected range).  First establish the meter reading with probes apart, then with probes touching directly to each other and note those readings.  THEN, you can connect the probes to the device to be measured and record the display indication.

I asked you to measure the resistance of the field coil.  There will be no voltage in the coil if it is disconnected from the bike.  So, a meter set to read voltage won't find any, and I can't use your report to help you.

Cheers,

[brcree]

OK Two...I'm not giving up that easy......Plugged field coil up ....on meeter there is a ohms section....with a dot with nothing by it, a dot with 20k/2000 next to it and then a dot with just 200. With key on the meter set to 200 reads 0.65.....meter set to dot with nothing reads 0.06.

[bollingball]

 I'm using a meter as well....and know how to use one.
[/quote]

[TwoTired]

Post a pic of your meter face.  Or, tell me the make and model of it. 

Sorry, I still can't interpret what you are telling me about your measurements in a meaningful way.

Cheers,

[brcree]

Not try-en to be a bugger there Two...just want this thing to run like it should....not much summer left! The meter is a Cen-Tech...item # 98025.

[TwoTired]

I'm trying to help.  But, electricity is unforgiving of vagaries or mistakes.  It's downright fascist in its demands.  You meet them or else!

Try this: set your meter selector to point to the Ω 200 section.
Place the probe tips together and note the reading.
Separate the probe tips and note the display reading.

Now, with the white and green wires disconnected from the Vreg connect them to the probes and note the reading on the meter's display.

Next place one probe on the green wire and the other on the case/cover of the alternator.
Next place one meter probe on the White wire and the other probe on the case/cover of the alternator.

Sorry if this sounds rigid and demanding, but electrical troubleshooting is like that.

Cheers,

[brcree]

No prob Two...rigid is ok....ok: green to white reading-9.0....green to case-1.3.....white to case-9.0

[TwoTired]

No prob Two...rigid is ok....ok: green to white reading-9.0....green to case-1.3.....white to case-9.0

Numbers don't add.
Green to case should be zero.  How could you get 9 Ω to case and Green from white when Green has 1.3Ω to case?

Place the probe tips together and note the reading.
Separate the probe tips and note the display reading.

For the CB750 the field coil is nominally 6.8Ω.  Which does not allow for much measurement inaccuracy.

I have to go out now for a few hours.  So, I'll be away from the computer for a bit.

Cheers,

[Spanner 1]

Were all messed-up here, folks. Poster we do not need 'key turned on'... were not testing for voltage here. No key on, por favor. We need to know if the field coil is good, which is tested thus;
The regulator has 3 wires to it. The white wire and the green wire go to the field coil. Disconnect them from the reg. and put your meter leads to white and green ( +,- doesn't matter to which lead ). Now, click your meter to it's lowest Ohms scale, (you report 200 ohms is the lowest 'click', we do not want the diode test setting, so stay @ 200 ohms scale ). What's the reading ?

[scottly]

also did a volt check across the g,w,and black wires on the reg.....g to w 0....g to b 9.5  with key on

Green to white should be the same voltage as the green to black. Your reading of 0 volts on the white terminal indicates a regulator problem, NOT a field problem. The contact points in the regulator should be checked and cleaned. Also, if you only have 9.5 volts at the black reg lead, you have a dead battery, or other problems in your electrical system. (I'm guessing run down battery)

[Spanner 1]

Scott, I believe he was testing with his meter on 'ohms' with the ignition 'on'...... above readings are not anything to go by....... as far as I can tell after re-reading his posts.... c'mon back OP !!

[brcree]

At the expense of making myself look stupid...and in this case i am....I would like to apologize to all for their time in trying to help an old fart out. Here was the prob.....maybe this will help others in the future. The Volt. Reg. wires were installed backwards........the metal cover was installed backwards sooo....the wires were as well. I didn't look to see the letters that were stamped on the tabs..........after looking at the schematic again...it hit me!!!!!!!!!! All is fine in Cafe land now...thanks again all for helping out an Ol Geeeezer.  Always remember....."KISS"...not the rock group...lol.