heres another test I did reading the VDC from each wire on the rectifier
(lights off/lights on)
Pink 11.8/11.6
Yellow 8.1/7.9 decreasing with RPM increase
Brown 11.5/10.2
Now heres the reading when I switch the brown wire with the pink wire at the connection from the stator to the wiring harness
Pink 11.8/11.6
Yellow 11.8/8.2
Brown 11.8/11.0
Over voltage
HSF,
I'm sorry but I'm confused here. How are you measuring DC volts on the stator? Are you touching each wire with one meter lead and touching the other meter lead to ground? The brown, yellow and pink wires are on the AC side of the rectifier. Not sure what kind of reading you would get with the meter set on DC volts. Set your meter on AC and measure across the brown and yellow wire terminals at the rectifier. The light switch will bring in the lighting coil (pink wire) onto the yellow wire when you switch on the lights so you will see it at the rectifier terminals. Then measure across either the black and green wire terminals on the rectifier or across the battery terminals with the meter set on DC volts. It is this DC voltage that you should see going up with rpm and raising battery terminal voltage. If the numbers you are reporting are reflective of what is coming out of the stator as AC, then I'm at a loss because I cannot explain why the voltage decreases with RPM unless that is the result of you measuring AC with the meter set on DC. If Wilf or G-man are reading this (and chuckling to themselves as I try to figure this out) am I correct in assuming that the AC output of the stator would be rougly twice what you would see out the DC side? I would think that the AC voltage is peak to peak and hence +12 and -12 would mean 24 volts AC, right? The other question I would have is, is there an error in the CB77 wiring diagram. It shows two coils connected to the pink wire and only 1 connected to the yellow. I would expect the reverse if the pink wire carries the lighting coil current. All this testing stuff aside, I just had a wild thought pop into my head. Is there any chance that you have the fused red wire from the battery and the unfused red wire switched and the fuse is blown? This would give you power to your lights but zero charging power to the battery because of the blown fuse. Just something to check here since you have had the harness apart before. And I'm sorry if I'm not 100% sure of how some of these components will function wrt their output. If I had not winterized all my bikes, I'd be running these tests on my 305 to see what I got for readings to compare to yours. regards, Rob
Hi,
For a good understanding of the stator please look at the thread "305 stator scheme, for anyone who's interested". So, looking again at your current measurements, between which points are you measuring ? Did you measure the coloured wires to ground ?, So pink to ground, yellow to ground and brown to ground ? How did you measure the voltage ? like Rob says, DC is not correct, should be AC. If measured ac with a DC meter, the outcome is unpredictable, but possibly around zero. Did you measure the voltage under load ? or free ? Did you measure the voltage to ground ?, or from pink to brown, pink to yellow, and yellow to brown ? Again, the currents you measured are making no sense. I have done intensive measuring of currents on these stators and I have never ever seen these currents, not even on a NOS set (high output CB72). Please answer the questions for a good understanding our side, so we can help you out. Solving Electrical problems are never difficult, but it should be clear what you measured and how. Jensen
assembly of Japanese motorcycles requires great peace of mind (Pirsig)
It's been a while but I remember seeing that alternator diagram before. I just traced out the circuits with a highlighter (only way to keep track) and it shows that the lighting coil is just the one pair of coils, which is how it is described. It looks like the picture in the wiring diagram is backwards and probably a bit misleading. So thanks for posting that. Need this stuff to jog some of my sleeping synapses back into operation.
I assume that the curve is for a typical 305 alternator. If so, it tells us that the charging current peaks at just under 5 amps at around 16 volts for 80 watts of power. That does make more sense when you consider how many riders look for LED bulb replacements to reduce the load on the charging system since rarely would you run at that peak power rating. regards, Rob I'm pretty certain that there is significant meter and/or measurement error behind all these funny numbers! I won't review them because I think the only way to advance toward a solution is to:
1. put all your wiring back together the way the circuit diagram shows (no more swapping of wires...) 2. carefully follow a deliberate, one step at a time process of elimination (I will help you with this) Before going ahead with any more measurements, cofirm that your meter is operating correctly. You said some time ago that the VDC reading at your battery was 3 or 4 volts too high--a very odd thing to be happening. You did say that you measured no DC current between battery negative and ground with the key off--that's good. The next thing to test is the AC voltage output of your stator. With all the wiring hooked up the way it should be, and with the engine running (lights off), meter set to AC volts and the meter leads connected to the two AC terminals on your rectifier (should be the yellow and the brown wires coming from the stator), record the AC volts at idle, 2000 and 4000 rpm. You can repeat the measurements with the headlight switched on. We'll go from there. Rob, I would expect about 18 VAC across the 2 AC rectifier terminals under light load (the meter should show peak AC, not peak-peak). I don't see anything wrong in the stator section of the schematic. The heaviest single load on the bike is the headlight so it makes sense to me that 2 pairs of coils would be added in parallel with the yellow pair when the headlight is switched in. Wilf Wilf,
I based my suspicion on the diagram being in error from the generic comments that the light switch adds the lighting coil (singular) to the charging circuit. Jensen's diagram also shows the majority (4 of 6) coils in the non-lights condition and the remaining 2 added with lights on. I agree with your approach of putting everything back together. I was surprised myself as to why HSF tore all the wiring apart. So, when looking at an AC sine wave, is the AC you measure with a DMM a function of the equation that determines the sine wave? After you corrected me, I remembered working with Peak AC reading on an outboard igntion system. You needed an adapter for a DMM to read Peak voltage. regards, Rob Hi Rob,
I refer to the stator wiring diagram that Jensen has recently posted. When I read it, it looks like the two coils at 10 o'clock and 4 o'clock are in series and provide a voltage between the Yellow and Brn (1 and 3 in the diagram) when the lights are off. The Pink (2} is a parallel connection of 2 o'clock and 6 o'clock and a corresponding parallel connection of 8 o'clock and 12 o'clock at the Brown (3) connector. This is consistent with the stator schematic showing 2 pairs of coils for the lighting function and 1 pair for the ignition function. If I'm reading this wrong, let me know! With respect to AC voltage measurements: just to be sure before posting something stupid (I've done that before!), I poked my reliable DMM into a 120 VAC outlet. It read 122 VAC (we're on a grid that varies quite a bit), and I know from looking at my oscilloscope that there's approx. +120 - -120 peak to peak. I'm curious to know how Jensen's diagram shows 2 pairs of coils being active in the "lights-off" condition.
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