RB108 regulator / cutout - 6 volt or 12?

[iansoady]

My recently acquired Golden Flash (1961) had a 12V battery and bulbs fitted, and an RB108 regulator / cutout unit. I had assumed that someone had attempted a "conversion" to 12V by just fitting the battery and bulbs - and the previous owner told me that the person before him had had a "charging problem". I'm reverting to 6V anyway, so am getting a 6V battery and bulbs.

I had thought that the RB108 was only a 6V unit but Googling it shows the RB108 listed as both 12 and 6 volts. Is there any way I can tell what I've got?

[trevinoz]

Ian,
        Normally the voltage is stamped into the back plate on these regulators.
As this is made of insulating material, sometimes the marks become obliterated.
An easy test is to run the engine and measure the output voltage with the battery disconnected.
Trev.

[iansoady]

Ian,
        Normally the voltage is stamped into the back plate on these regulators.
As this is made of insulating material, sometimes the marks become obliterated.

Spot on Trev. A judicious scrape with a wire brush and there is the 6V marking (along with a 59 which I guess is the year of manufacture).