Hugo.

Check out the manual (Part 1 Aircraft) page 76.  Start the GTC and the ATM,put ATM generator online and open GTC bleed air switch ,then check out the bleed air circuit breakers on the co pilot side circuit breaker panel. Make sure the circuit breakers are closed. If they are open this is your problem. If the cicuit breaker is open then there is no power to the switch.

John.