Charging questoins (Darmah)

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AndyCapp
Mariana
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Charging questoins (Darmah)

Post by AndyCapp » Sat Oct 01, 2011 8:57 am

Last time I was out, the "Gen" light came on. I checked the obvious things - earthing/loose connections etc first.

The next day, battery voltage was 12.9 - not too bad, so was this a generator/rectifier problem, or simply the voltage regulator falsely turning on the gen light? The Gen light should be off above 12.35v?

I did a battery voltage check, but my multimeter went wild when I started the engine - unable to settle on any value. So, I did a amp check and I was getting 7 to 8 charge amps at low-mid RPM. No too bad I thought.

Now the questions, for those with intimate knowledge.

From the wiring diagram , the voltage regulator seems to be a passive device - its job only to connect the gen light circuit to earth, thereby turning the light on. But does this device give any sense voltage back to the rectifier?

The 4-connector rectifiers have 2 generator inputs. The Red is the main charging line back to the battery, but what is the brown for? Is this a voltage sensing line - as it is only active when the ignition is on.

Are there any wiring diagrams (internal) available for the rectifier and voltage regulator?

Does anybody know where to get these small voltage regulators from ?

Thanks

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gioto3
Diana
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Location: Ferrara, Italy

Post by gioto3 » Sat Oct 01, 2011 11:12 pm

I had the same problem just one month ago in my SS darmah. After dismantling and checking all the electric connections I found some crappy contacts but didn't solve the issue.
I had quite good volt readings at the battery with engine turning and alternator supposed to recharge (see my previous post).
At the end I decided to test the voltmeter (the little red box you probably call regulator in your post) and found it faulty. It's a simple switch, from page 106 of the workshop manual "it automatically controls the off and on switching of the "GEN" warning light."
It turns on the warning light under 12.35 and over 15.7.
I ordered a new one at road and race, it's not in their web pages but Phil Hitchcock wrote me he still had five NOS. I still have to receive it so I can't yet tell you if I solved the problem.
Ciao
Giovanni
1980 Ducati 900 SS Darmah
1977 Ducati 125 six days
1972 Ducati 450 Scrambler
1953 Ducati 65 Sport
1949 Ducati CCC 60

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AndyCapp
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Post by AndyCapp » Sat Oct 01, 2011 11:36 pm

Yes, indeed the small red box - sometimes called a voltmeter, sometimes a volt regulator - but the important point is, it does not affect charging when it is not working? Its job is only to control the GEN light?

I might break it open over the winter, see what's inside and get a friend to put new components inside (it can't be too complicated)

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gioto3
Diana
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Location: Ferrara, Italy

Post by gioto3 » Sun Oct 02, 2011 10:28 am

It only controls the GEN warning light
1980 Ducati 900 SS Darmah
1977 Ducati 125 six days
1972 Ducati 450 Scrambler
1953 Ducati 65 Sport
1949 Ducati CCC 60

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AndyCapp
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Motoplat information

Post by AndyCapp » Sat Oct 08, 2011 5:43 am

I did some bench testing of my Motoplat Voltmeter.
At room temperature, it turns off between 12.4v and 15.5v. It draws 0.04A when the GEN light is off and 0.12A when ON. All well and good.

However, at ambient temperatures above 28c, the GEN light is permanently connected: the GEN light does not switch off. Since the unit normally sits above the engine, I think it would be difficult to insulate it.

It is proving impossible so far to find a replacement, so plan B is to make one. The electronic engineers where I am working at the moment can probably design a circuit for me. I will see if I can persuade one to build one in the same form factor as the original.

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gioto3
Diana
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Joined: Mon May 23, 2011 12:38 pm
Location: Ferrara, Italy

Post by gioto3 » Mon Oct 10, 2011 6:09 am

Just received my new voltmeter and once mounted all worked fine.
My old faulty voltmeter just seemed to act as yours cause it started to close the contact and so to maintain the warning light every time I was warming the engine and obviously it was the heat from the head that caused that, maybe reducing the gap between the poles of the electric switch operated by the voltmeter.
If you arrive to rebuild your just let me know cause I'm interested in trying to get it working again to have a spare part.
Ciao
Giovanni
1980 Ducati 900 SS Darmah
1977 Ducati 125 six days
1972 Ducati 450 Scrambler
1953 Ducati 65 Sport
1949 Ducati CCC 60

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AndyCapp
Mariana
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Joined: Fri Jun 10, 2011 10:30 pm

Post by AndyCapp » Mon Oct 10, 2011 7:54 am

I removed the epoxy resin from my unit. It is completely solid state, there are no mechanical parts. I have found somebody helpful who has offered to design a replacement circuit for me.

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AndyCapp
Mariana
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New unit using new components

Post by AndyCapp » Sat Nov 12, 2011 4:03 am

I have now designed and built a new voltmeter using new components - I have the netlist, PCB layouts and photos of the finished product. Would anybody like them? Can I upload them somewhere ?

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gioto3
Diana
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Joined: Mon May 23, 2011 12:38 pm
Location: Ferrara, Italy

Post by gioto3 » Sat Nov 12, 2011 9:42 am

Yes, I'd like to have your data and I suppose it should be of great interest for a lot of bevel and belt Ducati owners, should be the same in pantahs.
Maybe Steve can provide a place in the forum for that.
1980 Ducati 900 SS Darmah
1977 Ducati 125 six days
1972 Ducati 450 Scrambler
1953 Ducati 65 Sport
1949 Ducati CCC 60

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