I do not know the voltage regulator setup on 140, but thought I would pass this along. Hope you can use it to get going in the right direction.

Last evening I was reading an article on alternator testing/rebuilding (Internet, but don't recall address --- Google Search words: bosch alternator rebuild). One point mentioned is that if the brushes are bad or slip rings are worn, it can blow the voltage regulator.

I can't fully explain why this happens, but the brushes carry the current for the field winding. If it so happens that the contact between the brushes and slip rings is intermittant, when this circuit opens, the collapsing magnetic field will generate a large negative voltage which is potentially harmful to more than just the Voltage Regulator. This is the exact principal of the primary circuit of the ignition coil.

Dan