B4 lens control

This isn't really a BMD issue but hoped someone could give me some help...

Running BMD studio cameras w/ B4 lenses. I am powering the lenses of a 12V power converter. One day lenses are/servo's are fine...next day the zoom won't operate. Has no power...??

The power converters are brand new, at my wits end...

Thanks

Check your cables, sounds like a bad connection some where.
Cheers