Dynastart control box/regulator



My yacht's Volvo MD6A engine (1971) is fitted with a Bosch Dynastart. When throttled up, the ballast resistor(?) on the back of the control box is emitting a wisp of smoke and a slight burning smell. The voltage at the battery, which is fully charged, is 14v. On tickover, there is no smoke and 12.8v at the battery. The starter relay seems to be operating normally.

Any ideas (helpful) anybody?

Can replacements be found?

Thanks in anticipation.