Repair Help Please, Cobra Newbie

[Delawaredave]

Helping a friend. Unique 29 FIA, manufactured 1995.

First instance: was driving, turned on a number of electrical accessories (lights, electric radiator fan, etc) then when putting clutch in at stop sign, engine RPM would go low and then all electrical power cuts out - dash, headlights, etc. Engine stalled, car still rolling, so was able to let clutch out and "jump start" engine - and everything came back.

Then seemed to run fine if minimal electrical load (no lights, etc). The ampmeter seems moving normally - up to 30 amps under high engine RPM, down to zero, slightly positive at idle.

Second instance: same thing as above, but after engine stalled, pulled over to side of road. Car wouldn't start, no lights, gagues, nothing electrical. Pushed car home and still nothing when you turn the key.

Owner changed ignition switch (and says original one was fine also). Battery fine, 12.8 V. Master disconnect switch seems fine.

I don't have a schematic unfortunately. There must be a relay to send power to fuse block, right ? Where ? Maybe not energizing. But a bad relay wouldn't explain the "cut out at high electrical load" above.

Or voltage regulator ? But a bad voltage regulator would not explain why there's no electrical power when key turned on.

Hope this is complete background. Greatly appreciate any help!!!