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System Voltage

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Running my newly rebuilt '61 ES2, the voltage at the Wassel rectifier box out wires (with the rectifier disconnected from the battery/system)  is about 6-7 v at idling, but drops as the revs increase!!

Revving mildly - maybe 1500 rpm - it is about 5.8 V.

Is this possible? Does the fact that it is open circuit mean anything?

What have I done wrong?

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.. checked what the dynamo is putting out? Is the polarity correct? Those Wassell boxes have a poor reputation but some are OK - I had one fitted to a BSA A10 that worked fine. I assume by ope circuit you mean no battery connected which as far as I can see should make no difference.

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Yes, I have checked the stator (not a dynamo), three wires out give different ac voltages (kicking over fast only A-B = 2v, A-C=2v, B-C=0.5v). Suspicious?

So is the problem in the stator or the Wassell box?

I don't think it can be in the stator. The ac waves are converted to dc output in the rectifier box, so if one wave has a lower value, the rectifier dc output would be lower but would still increase with revs.

Any idea how I can test the (new) rectifier box?

Thanks for your help.

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The voltages your quote might be ok. two out of the three pairs gives an output -ok.                Trying to measure the AC has little meaning as the waveform is rubbish compared to that which your meter is calibrated for (mains, 50c/s) They should be different ie one a bit more than the other (with Lucas stator) but the two giving an o/p and not the third is fine. But what about a short to earth? There is an alternator test on my web site.

An alternator regulator/regulator should give a usable output with no load, but if you are using a cheap digital meter they will give a nonsense result as they pick up ignition interference.

If you want to return this reg/rect as faulty I can confirm it.

IAN S.no battery connected which as far as I can see should make no difference. Not quite right, the mechanical dynamo regulator does give an output with no load, the Vreg does not, it has to work with a battery. The Wassell dynamo regulator-no idea.

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.. I assumed it was a dynamo (didn't look at the year!).

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It's best to go for a higher capacity battery like Lucas specified in the 1950s.  Ignore the lectures about changing to 12 Volts because it's supposedly the best thing since sliced bread!  Let us dinosaurs riding our old nails stay original!

Anyway, I'm amazed when people talk of using batteries with a puny 4Ah capacity as they don't really have any place on a bike built since at least 1950 - probably earlier.  All you/we need is a Yuasa or similar B38-6A lead-acid battery which has a healthy 14Ah capacity.  As has been said, "modern" gel batteries don't necessarily last longer and the old bike's charging system is set up for lead-acid.

Run your system through a decent regulator like wot Al can supply and you'll be fine.  Obviously you can't ride at night outside of town because 6 Volt bulbs are only one candlepower! LOL!  Us old folk have night-vision eyes which must see into the infra-red so we don't have a problem!

 


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