Topic: Rectifier Regulator Smoked burned - could it be caused by

[Knightro]

Hey all,

I have a 78 CB750k. Points. 4 to 1 exhaust. Podz. After market Speedo Tach. Rest pretty much spec.

I was having blown fuses with old regulator rectifier (even though the guy I bought it from was using a 30amp, manual calls for a 15amp). Checked all wiring. Some brown spots (#30amp). Cleaned and tightened all contacts. Installed duo regulator rectifier from Vintagecb750.com. No instructions.

Installed it best I knew how. The one connector (5 point) color matched the connector to the rectifier. So used that connection. The other 2 colors were white/black and the physical body contact of reg/rect is the ground. I set it up as such color to color but it didn't charge or show any change when I blipped the throttle.

After trying all possibilities (that I could think of testing the diodes, testing stator) i decided to try something stupid and attach the black wire from the reg/rect to the white wire from bike and white wire from Reg/Rec to black wire from bike. Presto, it started showing a voltage change when I increased RPM.  Ran fine for a month. No problems what so ever. Battery stayed charged. Changed fuses to 15 7 3 as per manual (believe it was 3) and have not blown another fuse. (That being said, when I increased throttle, my multi meter said it only increased from just over 12v to about 13.2 V at best). None adjustable REg/REc

Recently i replaced the lights in my speed/tach's as they burned out presumably when I blew my fuses. The lights in them were 1.4w, 14V lights. That's what I replaced them with.

I rode bike like that for about 6 hours all together over a 2 day period. No problems.

final variable I can think of (and I know i'm going to get some comments, but please, don't worry about my taste, worry about the result) i purchased some 12V lights i wanted to try out as accent lights under the tank. These were in no way hooked up to the system and run off of a batter pack just for the test run. (i'm presuming this had nothing to do with my burned regulator, but here i sit with a burned regulator.)  It could have been that these insulated wires were near my ignition coils under the tank. Or contact with ground (frame) but again, not part of system, and fully insulated/no contact that I could see.

Why then after a day of riding, did my rectifier burn?

Could it be, black on white white on black, (i'd think this is obvious, except it didn't work the other/obvious way, and it did work this way for over a month with no loss of batter charge and no blown fuses.)

Could it be 14v lights. System not generating 14V at all. which force the regulator to push as hard as possible to support the 14V draw? I figured 13.5V would just be a little dimmer on the light, not blow my system. Should I have downgraded to a 12V light? Why did the speedo/tach come with 14V lights meant for a 12 V system? (rhetorical kinda)

Could it be my funny blue accent lights near the ignition coils? I'm certain this isn't part of the issue, but I don't want to burn too many more of these. It's not cheap. Also, I can set up my old regulator and rectifier as i know they still work, but if it is the 14V draw that is killing it i very well might just kill the OEM stuff. Don't want that.

Thoughts?

[BomberMann650]

Could hazard a guess that there are some ground fault issues.

[Knightro]

I should also add to my spec that there is a 55/60 watt headlight, it calls for 50-55 I believe max... (came with bike) I may have been running my high beams more last night than normal as well.

[Knightro]

was thinking ground fault, but the green cable, spec from oem Regulator which I believe is ground, I attached to the bolt/washer on reg/rec and also scratched off the paint on the reg/rec to improve contact. So it was double grounded or at least I took much precaution with the ground connection.

[BomberMann650]

was thinking ground fault, but the green cable, spec from oem Regulator which I believe is ground, I attached to the bolt/washer on reg/rec and also scratched off the paint on the reg/rec to improve contact. So it was double grounded or at least I took much precaution with the ground connection.

That could be your problem.

Rectifiers generally do not require frame ground.  The instructions that came with my Omp rect warned that contact with the frame or nearby structure would cause component failure.

Remember, a rectifiers job is to convert AC to DC.  Grouding your rect to a frame charged with AC while its trying to put DC to the battery is likely to create trouble.

[Bodi]

If, as can be assumed, there's a green ground wire, it should be connected to a solid frame ground. The other components - engine and battery primarily - must be well grounded to the frame as well. Repainted or powder coated frames can make that difficult. The battery cable connects to a motor mount bolt, at least one end should have the frame tab metal bare beneath it and on the engine side where it touches the case.
A reg/rect that grounds through its mounting bolts should NOT have instructions saying "don't ground it"... that would be unspeakably bad design. Some have exposed metal electronic components that should not touch ground.
VintageCB750 sells a few reg/rect models. Which did you get? All types look to have encapsulated electronics and a decent heatsink, grounding the case whether or not there's a ground wire is a good practice, shouldn't be an issue.

[scottly]

The other 2 colors were white/black and the physical body contact of reg/rect is the ground. I set it up as such color to color but it didn't charge or show any change when I blipped the throttle.

After trying all possibilities (that I could think of testing the diodes, testing stator) i decided to try something stupid and attach the black wire from the reg/rect to the white wire from bike and white wire from Reg/Rec to black wire from bike. Presto, it started showing a voltage change when I increased RPM.  Ran fine for a month. No problems what so ever. Battery stayed charged. Changed fuses to 15 7 3 as per manual (believe it was 3) and have not blown another fuse. (That being said, when I increased throttle, my multi meter said it only increased from just over 12v to about 13.2 V at best). None adjustable REg/REc

Why then after a day of riding, did my rectifier burn?

Could it be, black on white white on black, (i'd think this is obvious, except it didn't work the other/obvious way, and it did work this way for over a month with no loss of batter charge and no blown fuses.)

Yes, if you fried the reg it was most likely due to reversing the input and outputs of the reg. The charging system was not working properly if it only got up to 13.2V; it should have gotten up to about 14.5V.

[Knightro]

Thanks for reply.  Got reg/rec from vintagecb750.com.   No instructions version.  (Probably worth the extra 20$....      Model 73-0823 on that website. 

it ended up being a caltric model rr103. Not sure why but they sell them for freaking cheap.  Maybe that's the problem.   

[Knightro]

I've thought this much and confirmed by using continuity test on multi meter that the white on bike was going to generator and black had voltage change when key was on.   Believe this is the "on off" switch for the reg, but I'm not sure.   

Then why did it not work at all set up correctly but worked adequately reversed?


Guessing if it looks like that now it's shot eh?

[scottly]

Yes, the black wire is the on/off for the reg. Who knows how a reg will work (or fail) when it's connected incorrectly? 13.2V isn't adequate. BTW, the battery tray is isolated from ground via the rubber mounting grommets, so would not provide a ground to the case.

[Knightro]

Thanks Scotty.   I did all the tests on the rectifier when I got it in the mail but the interweb said I can't actually test the reg in a combo unit with home equipment. 
So I hooked it up and absolutely no change when I revved it. 

 Could it be that it was working so well on my new charge that it didn't 'need' voltage so didn't move with new charged battery etc?

Does a 55/60 watt bulb really mess with system?   

Would a 14v little light burn my reg/rec?

To be clear when I hooked it up correctly my battery died in 2 days.  When hooked up incorrectly it lasted over a month and a bit. 

When I hooked up OEM reg rec it worked great again.   

[scottly]

Does a 55/60 watt bulb really mess with system?
No, I've been using a 55/60 watt bulb on my 750 for over three decades  

Would a 14v little light burn my reg/rec?
No

[Knightro]

Thanks Scottly. I think it must have been grounding issues or faulty reg rec from day one.   

I have same rec on order.   Will post updates if same problem as before.  If not same problem and it worked my thoughts on this one being faulty from day one will be confirmed.   

Tbc

[Bodi]

I've seen these r/r units before, usually no problem. There are two types - power vs ground control of the field coil - but since they seem to specialize in SOHC4 Hondas it should be the correct type (power control).
The colors are the same as Honda OEM wiring harness colors - hopefully the functions match:
3 yellows go to the stator coil wires, also yellow.
Green is ground, a good frame ground should be better than plugging into a harness green.
Red is output, connect directly (no fuse) to battery "+", either the battery terminal or the solenoid input stud.
Black is switched power, black wire on the stock harness, there was one for the OEM regulator. This powers the regulator electronics and also (probably) provides the battery voltage reference to control output for proper charging.
White - controlled field coil output: this should be close to black wire voltage with key on but not running (field coil connected), float charging voltage is higher than the normal charged battery voltage so the regulator should be trying to get full alternator output. When the reference voltage gets to the set voltage, probably 14-14.5V, this should drop to a lower or zero voltage. That's what makes it difficult to test the regulator... you need a variable power supply to change the reference voltage - a battery connected will pretty much always have it asking for full output.

Make sure the field coil white in the harness actually connects to one of the field coil wires. The other coil wire goes to ground, somewhere in the harness. The coil itself has proven very durable and failures are super rare but measure its resistance (between the two wires) and then from the regulator wire to ground - these readings should be identical. There are a few connectors in the harness between regulator and coil, inspect and hopefully clean each of them. Same goes for the stator coil wires.

A 750 will handle a 55/60W headlight if the charging system is OK. Not if you use it with both beams lit though, some hi/lo switches allow that when the switch is put in a middle position.

[Knightro]

Great info thanks for the reply.   I will run some tests.  Hooked up the old rec reg and it is fine.  But rec is still hot like 101f.    With side cover of and brief city driving.   Will run tests with old system hooked up as it is a known working starter point.   And my new rec reg is not in yet.   On its way.

Probably need to check wires all the way back to the field coil to make sure everything is ticketyboo as you suggest.   

[b52bombardier1]

That 101 degrees F temperature is barely above human body temperature. And please understand that a rectifier is a somewhat lossy device that in proper operation dissipates some heat.

I think your rectifier is perfectly normal at 101 degrees F.

Rick

Sent from my SAMSUNG-SM-N900A using Tapatalk

[Knightro]

b52... fair enough. ...

So if my new rec burned, but my old OEM one is doing fine,  again, it seems the 'new one' may have been defective from the get go... in some way. maybe just deficient as it worked for a month. ...

Either way, i have new ones showing up in a couple days. (Hopefully) and i will be able to post (hopefully) positive outcomes. Thanks for all the info/comments.

 

[Knightro]

OK so I have recieved my new regulator rectifier.  But again... When I match colour to colour and the harness looks right it's just missing a green ground which I presume comes through frame.    But when I rev engine it barely moves the voltage meter.   

[Bodi]

The battery charges at a fairly constant voltage until fullycharged, at that point voltage will rise proportional to input amps - and the input power just turns the battery water into hydrogen and oxyge . So unless your battery is fully charged the result is normal. A fully charged battery is neede to test regulator Vmax cutoff.

[Knightro]

My battery sits now at 12.76v. I checked resistance and to confirm all wires lead to where they should lead.....    So.... If my battery is low it shouldn't crank up voltage production when I rev it? I thought that's exactly when it produces voltage... Or is my battery too high to trigger it?    Ugh.  I don't know how this works.  Lol.  Last time my battery died with my other rec reg.  Until I swatches up the wires black to white then it Linda worked for a month.   

To be clear when I rev engine my voltmeter I'm holding onto my battery terminals doesn't change.  Is this normal?

[Knightro]

Anybody?  I put the exact model # up above

[Knightro]

Ok now I'm confused....    One old timer says ground it.... One says don't.   

[Bodi]

A green wire is almost universally a ground wire. Even if the case is grounded there's no guarantee it will be mounted in a way to securely ground the case, so the wire is provided. It won't hurt to ground it regardless. Up to 1969 or so Honda did sometimes use green as a power wire but not in any SOHC4.
Check the voltage going to the field coil. It should be close to battery voltage with battery at 12.7V and drop almost to zero at around 14.5V at the battery.
Voltage OK? Check amps in the field coil circuit. Most meters should read up to 10A DC. That is enough. I don't know the exact reading you should have but around 5A is my guess.
That should produce full alternator output.
You can try disconnecting the battery "-" cable while running at 3000rpm or so, have the headlight on for a load though. You might get a voltage spike that blows ths headlight or other lamps but with an electronic regulator that works properly you shouldn't. Voltage should jump around but go up to no more than around 15V. If the motor dies immediately then the alternator is probably not working.
My point about the battery is that unless fully charged, voltage over its own it will be chemically converted into battery charge. Lead-acid batteries can soak a LOT of power when charging, the recommended charge current (usually Ah capacity/10)  is to avoid overheating and warping the plates and is not the maximum power it can absorb. The bike's alternator is not super powerful, it can't make more power than a good less-than-fully-charged battery can absorb. Voltage is held down by the battery until it is fully charged. Once charged, increased voltage causes electrolysis of the water ... "boiling" the battery, at roughly 15V+. The regulator tries to limit voltags to ~14.5V where the battery is happy, maintaining full charge but not electrolysing the water.
A perfectly working alternator will produce maximum current at 12.7 volts but any excess over system load (ignition and lighting) goes to charge the battery - until it's fully charged. Then voltage will go up until the regulator reduces field voltage - and thus alternator output - as voltage gets to 14.5V.

[Knightro]

Ok thanks.   My white sensor wire which was attached to the regularor and can be the only option as I can see it is showing no voltage at all.  I let my battery drop to about 11.7v to force it to throw volts and still no voltage change anywhere. 

I have yet to disconect the battery to test as you suggested but the fact I have no voltage at the white wire is already a concern. 

Will hook up my battery charger during the day while I'm away work to try and see if that is the problem maybe I am starting with to low a battery? But I just got it this year....   Then tonight I will try to disconect the bat while bike is running....   

[Knightro]

ok,

So that reg/rec from Vintagecb750.com isn't working. I am on my 3rd one. There is no power from the white wire to the stator/rotor. My rotor test came back with about 7.5 ohms so i'm thinking there are some bad connections there.

Going to get that opened up and check all the connections. The screws on the cover are super stuck. Gonna work on them slowly.

[Spanner 1]

Don't open your alternator !... if there is no voltage on the White wire from the reg/rect unit then no proof anything is wrong with the alternator ( very rarely is ). The Green wire from the rect/reg must be grounded as does the Green wire from the field coil. I would connect the R/R Green to the field Green that comes out of the alternator ( It's the green wire in the 8-way connector-has 3x yellow , white, light green/red and brown/red ) and MUST connect their junction to a solid ground .
7.5 ohms is a perfect reading for your field coil ( it's not a rotor ), so that's good .
I hope I'm explaining this good !... See the Green wire that comes out of the alternator goes to one end of the field coil winding ( White being the other end ) BUT the Green wire does not connect to ground in the alternator, it has to connect to ground externally, and it does in the stock wiring set up but NOT if you just connect it to the new R/R green which also must go to ground... phew 

[Knightro]

spanner one, thank you for your response. I would agree with your advice opening up that part of the bike should only happen if you really need to... I did before I read your post... realised I was able to test everything fine without doing that and my tests were coming back good.  That being said, my clymers manual says to open that puppy up to do any tests on it... bad advice... shame clymers.

SO, your post is a little confusing. You see my reg/rec up above, (i posted photo) there is only one green wire, and that fits into the stock wire block which before went to the stock rectifier... That is where the green ground field coil wire connects in the stock set up... ... or is this where i'm getting confused...
the green wire that would normally connect to the stock regulator (Which i thought went to ground, but is that the green that is supposed to connect to the field / green from the alternator/generator?  In my new reg/rec there is no connector for that green ground which was before on the stock regulator. The best I can find online is that the unit grounds through the body of the reg/rec. So I have taken that green wire from the old regulator, put a different connector on it so that it fits nicely onto a mounting bold for the reg/rec and i'm using that as the ground at this point for the reg/rec. (though, again, I can't get it to work properly when set up this way)....   YOU say that field coil wire should not go into the block connector but that it should go straight to ground, and then i presume you suggest the green wire from the reg/rec should also go straight to ground?  Have you used this reg/rec before? and that set up worked?

After reading my response is it more clear what i'm doing wrong/right?

others suggested it was a ground issue early in this thread.... All my grounds have very low resistance...    .002  or .0018.

[Knightro]

I did want to mention here, though this sounds like a plug, it is just a fact... www.vintagecb750.com the place I got the original reg/rec combo unit which started smoking... has responded to my complaint. They are sending me a  Rick's Electric with instructions. they said if that one burns, its cause of my bike, but i think my bike checks out... so I hope this is all because of a bad reg/rec. ...

Still. I now have 2 of these reg/recs and I would like to just get it to work... especially seeing as how I have another old bike that could use an update.

So I have to say, I am very happy with Vintagecb750 and would recommend them to anyone especially a Canadian as they are in Canada, we don't pay duty but we do pay american which is a pain in the but...

[Spanner 1]

That R/R unit does not ground thru' the case mounting screws, that's why it has a green wire needing to be connected to ground. Same with the field coil green, it must be connected to ground.

Lets recap on what wires go where. First cut off that white connector.
The 3x yellow go to the 3x yellow in the 8-way connector ( the half of the connector whos wires go into the alternator ).
The Green wire goes to ground.
The Red wire goes to the battery +
The Black wire goes to any convenient Black wire on the bike
The White wire goes to the White wire in the ^ above connector and
The Green wire in the ^ above connector also goes to ground 

[Knightro]

thank you for the clarification.

one last thing which may be causing my rec/reg to burn out... is this tidbit of info which I get from Ricks motorsport electrics.... however I don't really see a 'cause/fix' anywhere for this occurrence.

The occurrence is this:
- The voltage on the black sensor feed wire is greater than a .4Volt drop from the voltage reading I'm getting between the batter terminals. It's more like a .6v drop. that from what I understand, will cause my alternator/rec/reg to constantly try to send increased voltage to the battery. causing early fault in the battery and possibly burn out the Reg/Rec.

I believe the info I have says this is due to loose or corroded connection somewhere on that black sensor wire... but that is part of my whole bike harness....    Is the fix for this simply running a fresh wire from ignition hot (black wire) to somewhere on the bike... somewhere ... remains to be determined by me...

Or am I missing something...

[TwoTired]

What you are missing is attention to all the connectors and switch contacts between the battery and the black wire connection to the regulator.

Cheers,