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Old 11-15-2013, 11:42 AM   #1
mntbkrguy OP
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Rectifier vs. Regulator

I have an 82 Suzuki SP500 I am bringing back to life. It runs now but I have no lights, blinker, etc. The bike has a 6 volt system with a seperate regulator and rectifier. I have been digging through a bunch of different threads and I understand that the regulator keeps the voltage consistant and the rectifier changes the current from AC to DC.

Correct me if I am wrong but I believe my problem should be with the rectifier since it has spark and it needs to covert the power from AC to DC just for the battery and lights. Is my logic sound?
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Old 11-15-2013, 12:51 PM   #2
NJ-Brett
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There is no logic.
The bike might have a cdi system, which does not need a rectifier or regulator, it has its own stuff built in.

Easy to test some parts:
Start the bike, measure the voltage (AC) out of the stator coil/coils.
Measure the rectifier on the diode check or low ohms scale of a meter.
Measure the voltage (if any) before and after the rectifier.
Most old small bikes were single phaze, so the rectifier is just a (single)diode.

The regulator is harder to test, depending on how it works and how its wired into the system.
On my old XT200, its across part of the stator coil, and shorts out above some voltage, but its not at 6 volts I think.
They also used one system for the battery stuff (brake light, neutral light, turn signals) and another for the headlight.

If you have no stator output, you will have no 6 volts.
If the rectifier is bad, you will also have no 6 volts.
If a ground is off someplace, you will also have no 6 volts.

Quote:
Originally Posted by mntbkrguy View Post
I have an 82 Suzuki SP500 I am bringing back to life. It runs now but I have no lights, blinker, etc. The bike has a 6 volt system with a seperate regulator and rectifier. I have been digging through a bunch of different threads and I understand that the regulator keeps the voltage consistant and the rectifier changes the current from AC to DC.

Correct me if I am wrong but I believe my problem should be with the rectifier since it has spark and it needs to covert the power from AC to DC just for the battery and lights. Is my logic sound?
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Old 11-16-2013, 01:44 PM   #3
aduthie
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Quote:
Originally Posted by mntbkrguy View Post
I have an 82 Suzuki SP500 I am bringing back to life. It runs now but I have no lights, blinker, etc.
In general, if you have a fully charged battery in place and turn on the ignition switch and headlight switch, the lights will work, at least until they run your battery down. Off road bikes change a couple parts of that formula, though.

Here's a wiring diagram that should match your bike:
http://www.advrider.com/forums/attac...1&d=1327538044

There is at least one error in the diagram, but it looks like the orange ("O") wire will be 6V+ as long as the ignition switch is on and works properly. Once the orange wire is hot, functional brake switches should send power to the brake light. If you turn on the headlight switch, that should get the taillight working, too.

The headlight appears to be powered separately by a single-winding stator inside the engine. The P and W/R wires. These are connected to the headlight via that headlight switch (same switch, separate circuit from the taillight) and regulated by the... well, by the regulator. Note that if the engine's not running, the headlight's not getting power, no matter what. This is not true of the DC-operated taillight and turn signals, which only require the battery.

For a long story short, it kinda sounds like either your fuse or your taillight bulb is bad. That doesn't explain the headlight, though, so you may have a couple problems.

If your rectifier or its wiring is bad, your taillight will work fine after you charge the battery, but the battery will go dead as you ride, leading to a dim (at best) taillight after a while.

Other lights that work from the battery: neutral light, turn signal indicator.

Other lights that work from the AC generator (with the headlight): speedometer backlight, tachometer backlight, high beam indicator.
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Old 11-16-2013, 03:38 PM   #4
NJ-Brett
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That sounds about the same as my 1982 xt200, and the ignition system is cdi which does it own thing apart from any lights/battery.
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Old 11-16-2013, 08:42 PM   #5
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A single phase rectifier will not be a single diode. Most likely it will be four diodes (full-wave bridge) or at the very least two diodes.

A schematic for a typical single phase motorcycle rectifier will resemble this:




The squiggly line on the left of the diodes would represent the alternator.
The stuff on the lower right doesn't correspond directly to any part of a motorcycle electrical system, this just happens to be the best illustration of a bridge rectifier that I could scrounge up on short notice.

If your bike has a spark, it's possible that the ignition uses a magneto, which generates its own voltage, or that the ignition is ac, which is tapped off the alternator prior to the rectifier (yes, some older bikes used such a system).
Look for ac voltage on the input (probably two yellow wires) to the rectifier, and dc voltage on the output.
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Old 11-17-2013, 06:50 AM   #6
aduthie
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The SP500 uses a single diode rectifier. See the wiring diagram in post #3, straight from Suzuki.
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Old 11-17-2013, 07:17 AM   #7
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Quote:
Originally Posted by aduthie View Post
The SP500 uses a single diode rectifier. See the wiring diagram in post #3, straight from Suzuki.
Given that the ignition is by magneto, and the headlight is powered directly by the ac ouput of the alternator, it isn't surprising that a half-wave rectifier would be considered suitable to provide the trivial amount of current required by the remaining accessories.
What surprises me is that any Japanese manufacturer would have been using such a primitive system as late as 1982. That's more appropriate for Lucas or some of the Italian companies in the 1950's.

(Edit) Add one more mistake in that diagram; that's not a magneto, it's the alternator. I guess technical writers in Japan were still struggling with English as late as 1982!
But it makes it even more amazing that they used a half-wave recifier, given that the ignition was also running off the dc side of the system.

caponerd screwed with this post 11-17-2013 at 07:35 AM
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Old 11-17-2013, 03:38 PM   #8
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Originally Posted by caponerd View Post
But it makes it even more amazing that they used a half-wave recifier, given that the ignition was also running off the dc side of the system.
Ah, look again. The ignition is CDI, running off a source coil and a pulser coil. Brown and Gray wires are the source coil to energize the CDI's capacitor, and Green and Orange from the pulser coil to tell it when to fire. (Suzuki doesn't do a very good job of keeping wire colors separate, so although most of the orange wire in the diagram is 6V+ with ignition, this other orange wire is one half of the pulser coil output to the CDI module. Thanks, Suzuki!)

As for the half-wave, single-diode rectifier... Beats me. "Dirt bike" is usually a good excuse for things. Hell, the bike is even a 6V, but even Honda still had some 6V bikes at least as late as 1981, so Suzuki wasn't alone, there.
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Old 11-19-2013, 07:53 AM   #9
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Clearly I have more testing to do. I have a new battery that is charged but I have not had it on the bike while running. I got the battery, charged it and turned the key but had no power. I checked the single inline fuse and it is fine but didn't go any further since I had spark. Getting it started was the first priority. Now that it runs I will hook the battery back up and start the testing listed in the service manual. I do not have a very strong background in electronics so I really have to concentrate to understand what you are explaining above. lol

I just posted the question thinking it was a simple problem which people have run into on other bikes with similar electrical systems based off of other posts. I guess I was wrong. Thank you for the information, when I get time I will run the tests and probably have more questions.
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Old 11-19-2013, 10:43 AM   #10
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That would be nice, but I got a half wave rectifier setup, one side of the magneto coil is grounded, single diode on the other wire gives 6 volts (on a good day). No regulation at all that I can tell.


The old Triumphs had a full wave setup like you show, with the zeiner diode clamp/regulator.

Then you have the multi phaze setups...




Quote:
Originally Posted by caponerd View Post
A single phase rectifier will not be a single diode. Most likely it will be four diodes (full-wave bridge) or at the very least two diodes.

A schematic for a typical single phase motorcycle rectifier will resemble this:




The squiggly line on the left of the diodes would represent the alternator.
The stuff on the lower right doesn't correspond directly to any part of a motorcycle electrical system, this just happens to be the best illustration of a bridge rectifier that I could scrounge up on short notice.

If your bike has a spark, it's possible that the ignition uses a magneto, which generates its own voltage, or that the ignition is ac, which is tapped off the alternator prior to the rectifier (yes, some older bikes used such a system).
Look for ac voltage on the input (probably two yellow wires) to the rectifier, and dc voltage on the output.
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Old 11-19-2013, 10:51 AM   #11
NJ-Brett
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No power to what?
Only the brake light, and maybe the trun signals work off the battery, along with the neutral light.

If you have a good ground at the battery, power goes to main fuse, to key switch, to bulbs, then to ground.

Make sure the brake light has a good ground.
The neutral light has 6 volts all the time and gets its ground through the switch inside the motor.
Also be sure to check the bulbs, all the bulbs were blown or missing on my xt.
6 volt bulbs can be hard to find....
Its been a long time since anything had a 6 volt headlight...


Quote:
Originally Posted by mntbkrguy View Post
Clearly I have more testing to do. I have a new battery that is charged but I have not had it on the bike while running. I got the battery, charged it and turned the key but had no power. I checked the single inline fuse and it is fine but didn't go any further since I had spark. Getting it started was the first priority. Now that it runs I will hook the battery back up and start the testing listed in the service manual. I do not have a very strong background in electronics so I really have to concentrate to understand what you are explaining above. lol

I just posted the question thinking it was a simple problem which people have run into on other bikes with similar electrical systems based off of other posts. I guess I was wrong. Thank you for the information, when I get time I will run the tests and probably have more questions.
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Old 11-20-2013, 08:02 AM   #12
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Quote:
No power to what?
Only the brake light, and maybe the trun signals work off the battery, along with the neutral light.
I have no power to anyhing other than spark on the engine. That means no headlight, taillight, guage lights. More research will be done when I am off from work on Friday and I will provide an update.
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Old 11-21-2013, 05:39 AM   #13
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I think I solved the obvious problems. I got a chance to play with it last night and tested each light bulb on the bike from the wires toward the battery. I learned it is difficult to tell if you have a burnt out headlight on these old bulbs. There was no dark stains or discoloration both the filaments were just not there. I could only tell by tilting it at just the right angle (and the fact that it didn't light up with direct contact to the battery). I believe the symptom of no power was just a combination of several very little simple problems, bad grounds burnt out bulbs etc. Inside the taillight was a complete mess so need to completely rewire that. The PO swapped out the old metal taillight/plate mount for what is really just a big thick piece of flat rubber, it kind of looks like a piece of conveyor belt. It looks like it is to prevent the taillight/plate from getting bent up so it's worth keeping. you can see it below in the pic.



I did notice that the neutral, and high beam light on the gauge did not come on but the high beam is probably because the headlight was disconnected and the bike was not running which would explain the neutral light. Am I correct there? I didn't check those bulbs so that is something to deal with after getting a new headlight.

Thank you for all the input I have a little better understanding of what makes up the electrical system now.
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