direct replacement 6 Volt rectifier for Monza

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ranton_rambler
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Location: Stafford UK

Re: direct replacement 6 Volt rectifier for Monza

Postby ranton_rambler » Sun Feb 11, 2018 10:23 pm

Maybe mine isn't the 60W version, it only has 2 coils I think. Will try and find a photo later in the week, and remind myself what resistance I measured.
Ian

ducwiz
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Re: direct replacement 6 Volt rectifier for Monza

Postby ducwiz » Mon Feb 12, 2018 7:20 pm

The "black brick" R-R fits only the 60W alternator which was used in all the 250 and 350 n/c models, except the Mark3, featuring the 40W alternator without any regulator. The latter cannot combined on any condition with the 60W type. So, if your bike is a 200cc or even smaller, the black brick is useless for you.

cheers Hans

double diamond
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Re: direct replacement 6 Volt rectifier for Monza

Postby double diamond » Mon Feb 12, 2018 7:32 pm

The early models (175/200) with a battery ignition used a plate type selenium rectifier made by Westinghouse but no regulator. I’ve seen several Ducati systems that incorporated a Honda 6v plate rectifier as a replacement.

Matt

ranton_rambler
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Location: Stafford UK

Re: direct replacement 6 Volt rectifier for Monza

Postby ranton_rambler » Mon Feb 12, 2018 8:47 pm

The bike was in bits when I got it, but the previous owner bought it complete (albeit a non-runner) and took it apart.
Here's the stator:
DSCF5241small.jpg

and the regulator/rectifier (with the cover and rectifier removed):
DSCF5219small.jpg


I did the tests described elsewhere on this forum and concluded the diodes are dead.
The stator coils are both 0.7 ohm to ground.
The rotor has part number 4421.4003 stamped on it.
DSCF2905small.jpg


Sounds like this is a mismatched set of parts?

Buster
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Location: Reading, UK.

Re: direct replacement 6 Volt rectifier for Monza

Postby Buster » Mon Feb 12, 2018 10:06 pm

If you are going for originality ignore this, if not have a look at Electrexworld website, whole kit converts to 12volt and many amps........by a happy converter.

ducwiz
Posts: 266
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Location: near Frankfurt, Germany

Re: direct replacement 6 Volt rectifier for Monza

Postby ducwiz » Tue Feb 13, 2018 9:22 am

ranton_rambler wrote:The bike was in bits when I got it, but the previous owner bought it complete (albeit a non-runner) and took it apart.
Here's the stator:
DSCF5241small.jpg
and the regulator/rectifier (with the cover and rectifier removed):
DSCF5219small.jpg

I did the tests described elsewhere on this forum and concluded the diodes are dead.
The stator coils are both 0.7 ohm to ground.
The rotor has part number 4421.4003 stamped on it.
DSCF2905small.jpg

Sounds like this is a mismatched set of parts?


I suppose your bike is a 175 or 200, you didn't mention that before. Again - referring to the ws manual, these bike usually did not come with the black brick R-R. So, your bike might be modified. How many wires come from the stator, 2 or 3 ? If there are only two, your alternator can be one like this here https://www.ebay.de/itm/Komplette-Lichtmaschine-fuer-Ducati-Koenigswelle-1Zylinder-fruehe-Modelle-zB-SCR-/232556127536?nma=true&si=l1S6PmQQlKtjTrHbztzhXfWOMfo%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557, rotor no. at least is identical. It might fit together with your R-R, anyhow. As one can see in the fotos, each of the coils is grounded at one end, likewise the 60W alternator. The 40 (or 28 W) types known to me come with one coil grounded, the other floating, hence 3 wires come from the stator.
This thread stays thrilling somehow.

cheers Hans

EDIT:
- the only alternator of this 2-wire type known to me is that of the 450 R/T, but this has different wire colors
- the electronic R_R offered by Guzzino might do the job for you

Ventodue
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Location: Montpellier, France

Re: direct replacement 6 Volt rectifier for Monza

Postby Ventodue » Wed Feb 14, 2018 11:05 am

ducwiz wrote: ... your alternator can be one like this here https://www.ebay.de/itm/Komplette-Lichtmaschine-fuer-Ducati-Koenigswelle-1Zylinder-fruehe-Modelle-zB-SCR-/232556127536?nma=true&si=l1S6PmQQlKtjTrHbztzhXfWOMfo%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557 <snip>

... the only alternator of this 2-wire type known to me is that of the 450 R/T


Pretty sure you're right, Hans - that ebay item is a R/T stator (2 coils, 2 wires).

Image

Ventodue
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Re: direct replacement 6 Volt rectifier for Monza

Postby Ventodue » Wed Feb 14, 2018 11:22 am

Ventodue wrote:
el_guru wrote: ..as its extremely simple and basic system it doesn't even regulate the voltage...!!!

You SURE about that? Not so, according to the article that Hans linked to.

Just to get back to this, and hopefully forestall any repetition of any misunderstanding.

This device is indeed both a rectifier AND a regulator. It's even described as such in the parts book (if the presence of those 3 coils isn't already enuf evidence ... :roll: ).

I quote from page 37: " Rectifier and current static regulator 6V-10A-34.72.13".

In practice, it probably doesn't make much difference as the alternator is rarely going to spit out enuf juice to boil the battery. But that's no reason not to put the record straight ... ;)

Craig

ranton_rambler
Posts: 135
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Location: Stafford UK

Re: direct replacement 6 Volt rectifier for Monza

Postby ranton_rambler » Wed Feb 14, 2018 7:02 pm

I fetched my generator inside and had another look at it. The rotor is the same as the one in the eBay ad, with 4 magnets.
The stator is similar, but mine has the 2 coils wired a bit differently, with a couple of wires bridging across between the 2 coils at the opposite end to the wires going out to the world. Both coils appear to be grounded at one end, with 2 yellow wires going out. I think I'll need to remove the coils and replace all the wires so maybe can work it out better when I do that.

I was planning to switch to LED bulbs, convert to 12V and buy a modern regulator, if the stator is OK, but I won't know until I have the engine back together and running. Main reason is the cost of the replacement generator - not too excessive but this little bike is showing a real ability to make me spend money.

It's a 175TS from 1961 judging by the date stamp on the fork leg, so maybe later n/c bikes have different electrics from the earlier ones?

ducwiz
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Location: near Frankfurt, Germany

Re: direct replacement 6 Volt rectifier for Monza

Postby ducwiz » Wed Feb 14, 2018 8:40 pm

A manual for the early n/c singles (125 - 200) is kept here http://s5.histats.com/stats/r.php?104172&100&58&urlr=&www.rpw.it/Files/Ducati_Motoleggere_Monoalbero_ManOff.pdf for download, but beware: ~63 MB size, italian lang.
No link for a downloadable manual for the later n/c's (160 - 350) known to me, but I can send one on request 25/32 MB size, english

In both of them the different electric systems are described. And again: no 2-coil stator with only 2 wires appears in any of the schematics there.

I was planning to switch to LED bulbs, convert to 12V and buy a modern regulator, if the stator is OK, but I won't know until I have the engine back together and running. Main reason is the cost of the replacement generator - not too excessive but this little bike is showing a real ability to make me spend money.


I'm in doubt that this weak alternator (afaik 28 Watts) has enough power a low revs for a 12V conversion.
Just for reference the circuit schem. of the 450 R/T (magneto ignition and AC lighting, no battery, stop light, horn):

Image

Hans
Last edited by ducwiz on Wed Feb 14, 2018 8:41 pm, edited 1 time in total.


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