175TS with 125S engine project

[Jordan]

I believe selenium diodes have more forward voltage drop than silicon diodes, hence the lower efficiency.

I stand corrected.
I was thinking of germanium diodes.

[Ventodue]

Searching the forum yesterday I found a wiring diagram in the Italian manual that was more clear than my copy <snip>

Hi George,

Bit late on this, for which my apologies; but attached mainly for interest is the wiring diagram for the Spanish 125s, 175s and 200s.

It does differ visually at least from the Bologna 125 & 175 diagrams I have. But whether these differences are purely graphical or are indeed electrically different ... Ah that, I admit, I haven't checked .

Saludos

Craig

[Ventodue]

<snip>
As I have it wired up, the following applies with engine stopped:
Ignition on, Headlight switch off, brake light and horn operates ... <snip>

From the owner's handbook, this is what should happen.

Notes:
1. I have lightly edited the text to make more readable. But it's easy enuf to translate so I haven't bothered
2. 'Luz de ciudad' in situation 3 & 5 is what we usually refer to as a pilot light. 'Faro pilota' is the rear light.
3. Note the change-over between the coils that occurs in situation 4.
-------------------------------------------------------------------------------------------------
FUNCIONAMIENTO

1. Estacionamiento diurno
Llave desconectada. Conmutador en posición 0.

• El vehículo no se pone en marcha.
• La conexión rectificador-batería esta interrumpida.
• Lámpara de control del encendido, color rojo, apagada.
• Desconectados claxon, encendido motor y luz principal.

2. Circulación diurna
Llave conectada. Conmutador en posición 0.

• Lámpara de control encendido motor, color rojo, encendida.
• La batería se carga por medio de la bobina Vl que corresponde a ½ de la carga = Amp. 3.

3. Circulación nocturna ciudad
Llave conectada. Conmutador en posición 1.

• Están encendidas: luz de ciudad y faro piloto. Lámpara control verde encendida.
• La batería se carga por medio de la bobina Vl que corresponde a ½ de la carga = Amp. 3.

4. Circulación nocturna carretera
Llave conectada. Conmutador en posición 2.

• Esta encendida la luz principal (6,3V 25/25W).
• La batería es cargada por medio de la bobina A, que corresponde a la carga máxima de Amp. 6,5.

5. Estacionamiento nocturno
Llave desconectada. Conmutador en posición 1.

• El vehículo no se pone en marcha.
• Desconectados claxon, encendido motor y luz principal.
• Estan encendidas luz de ciudad y faro piloto.
• Lámpara control verde encendida.

[George]

Hi Craig. thanks for information. I have established by stripping cable outer covering that I have three wire alternator 1 yellow 1red 1 white.
My problem is that white wire was discoloured and I made the mistake of thinking it was yellow and soldered new cable 2 yellow and 1 red to coil. Motorcycle reassembled an run for about 12 miles, battery gassing up indicating either rectifier faulty or stator yellow / white wires connected wrong
I have ordered replacement rectifier.
The red would of been soldered in correct to coil. I now have two yellows, one of them is soldered to coil white connection and I have no way of knowing which is which even if I removed rotor there is no indication on stator coils. Are there any tests that you know of that I can confirm correct wire, yellow to rectifier AC, white to 'A' in headlight connector then to main switch and what would be the result of wiring wrong way round.
If anyone has an alternator stator in their workshop same as image below, taken before removing, and wires are still attached could you please check how wires are connected
Refresher engine is early 1960s Mototrans 125TS.
Thanks in advance

[Jon Pegler]

The Spanish wiring diagram shows a red, a white and a yellow wire from the alternator.

[George]

The Spanish wiring diagram shows a red, a white and a yellow wire from the alternator.

Hi Jon thanks for reply. Does that mean that white and red wires connect to top coil shown in my photo and yellow wire is connected to bottom coil in my photo?
if so would white and yellow wires have different resistance coil to earth or would you know of a way of testing which of my two new yellow wires should be white without stripping bike down.

[George]

Looking at excellent wiring diagram supplied by Jon it would seem that white wire is connected part way along top coil and my reasoning is that this should have a lower resistance than yellow to red. My readings are: Yellow 1 to red = 0.5 ohms. Yellow 2 to red = 0.7 ohms.
If my theory is correct this would indicate that yellow 1 is the white connection.
If there is anyone with a better understanding of Ducati electrics than me, that's just about everybody, I would be obliged if they could confirm my theory is correct or not as this will save me removing left side, clutch and rotor

[veloduke]

George

I agree with your reasoning regarding resistances.

I am going to read the manual again to try and understand what's going on. For some reason I was expecting the red and white wires to be swapped from where they are. . It would be good to actually see one with the wires exposed.

I'll have to go throught the electrical tests for my own peace of mind. I haven't run out of volts yet, so it must be working. Just need to make sure that I'm not overcharging the battery.

Meantime, here's a picture of my installed rectifier. Note how one terminal is at 90 degrees to the others - that's the +ve output. The terminal diagonally opposite is the -ve output. The other two can be either way around. The rectifier body should be disconnected from any of the four terminals, so all four terminals need connecting.

[George]

Thanks for reply and photo of rectifier Max.
If my reasoning is correct then I had installed white and yellow the wrong way round and this may explain why my battery was spitting out liquid, overcharging. The other thing I noticed when bike is running and headlight on, headlight did not change brightness when increasing revs and from what I read in manual battery should only get a trickle charge. I have changed white and yellow wires over and will connect rectifier as you have shown when it arrives. After starting bike I will check voltage across battery which I believe should show 6.6 volts with headlight on. Does this all make sense to you

[Ventodue]

Looking at excellent wiring diagram supplied by Jon, it would seem that white wire is connected part way along top coil and my reasoning is that this should have a lower resistance than yellow to red. My readings are: Yellow 1 to red = 0.5 ohms. Yellow 2 to red = 0.7 ohms. If my theory is correct, this would indicate that yellow 1 is the white connection.

Hi George,

You're right to think that one of the coils of the 40W narrow-case stator, be it Italian, be it Spanish, is double wound. This purpose of this double winding is to allow the power supplied to the battery to match demand, i.e. depending on whether the headlamp is on or off.

To do this, the winding that the white wire is connected to is switched in or out by the main switch. In positions 0 and 1 = head light off, it's out. In position 2 = headlight on, it's in.

Unfortunately I haven't as yet found any resistance values for these two windings which might enable you to determine which wire is currently (no pun intended ...) connected to which winding. (DewCatTea Bob gave target values for the 28W stator; but even if the 28W and the 40W look quite similar, they're wired quite differently).

If I come up with a revelation overnight, be assured I'll let you know ...