Regulator for a dynamo

ANY modern dynamo (and alternator for that matter) regulator cannot be quizzed with a multi-meter for anything useful/intelligent. The manufacturer of such items might be able to tell something , but not us users. But As a seller of these things I can test the ones I sell. 

The wire colours you have do NOT appear to be one of ours so I can't help you but any decent piece of equipment should/must have technical backup. A 1957 bike would be on the cusp of going alternator by the way. Please check aoservices.co.uk for our regulator and its connections.

It is reasonable to 'assume' that the BLK and RED are battery orientated. But as the dynamo has an output relative to earth then the whole plot needs to be 'relative to earth' So such dynamo regulators need to be know, is it Positive or Negative earth? The electronics inside such things are not forgiving!! Any manufacture of such device needs to mark the Polarity and the wire connections.

Bear in mind that I am always going on about wiring colours within our bikes. From 1963 it was standardised. If we stick to this then we know where we are if you use pink and purples and red connects to Black on your bike-expect smoke and lack of functionality. A standard for dynamos has been GRN for Field and YLW for Dynamo output.

Alternator regulator/rectifiers are not concerned with the polarity of earth as the alternator is NOT earthed.

hello

i had a 3 wire regulator on my bike / dynamo 12 volt positive earth.

colour of the wires coming out of the unit are.

black.. to.. Amp meter

green  to.. field

blue to D

assume the earth connection was picked up through the metal case bolts.

its a gamble if you connect yours and it blows. but how would you use it, if you cant test it. and be sure its wired correctly.

at the time i had a look inside the one i have,you cant see anything for clues as its set in a resin of sorts

barry

It is almost certain that the three wire regulator was a JG unit from the 1980s, these had three wires and picked up the earth through the case. IN the 1980s this was the only option to get 12V from the 6V dynamo. For a while they were reasonable successful. One major point to note with the JG was the change inside the dynamo from Field to earth TO Field to live. Field to Earth is the Lucas connection. Field to Live is a bosch connection. please be aware that ALL the rest of the world seems to have used Field to Live, Bosch, Italy, China, USA. Only us English used Field to Earth which is Lucas. So now you know. Be-wary. The AO Services unit is for LUCAS only. As it happens most dynamos can be converted from one type to the other. BUT it is important you understand what you are trying to do. Otherwise you do NOT have anything working. Details on my web site, or talk to your friendly Dynamo repair man.

there may be a local person who has one of these regulators fitted to a bike.  Ask around, maybe ask family members of the maker if they know of one sold / fitted to a bike.