A B757's autopilot computer servo circuit breaker popped at 3;500 FT; the number two autopilot disconnected with the autopilot warning light and the aircraft pitched up 10-15 degrees causing a 30 KT airspeed loss.

Narrative

Departed the airport on a clear sunny day via an RNAV SID. Had just cleaned up the aircraft and were proceeding to the initial waypoint on the RNAV departure off Runway 27. The center autopilot was engaged with LNAV and VNAV selected. We were climbing normally through about 3;500 MSL (2;500 AGL) to 10;000 MSL at about one mile prior to initial waypoint when we got an aural warning horn and an autopilot warning light indicating that the autopilot had malfunctioned and or disconnected. The aircraft immediately pitched up about 10-15 degrees above the normal climb pitch and quickly lost about 30 KTS (230 down to 200 KTS) of airspeed before I ensured the autopilot was disconnected; leveled the wings and lowered the nose back to a normal pitch attitude. As we recovered and made sure the aircraft was flying normally without the autopilot; we inadvertently missed the left turn as we passed the waypoint on the departure. We started the turn about a mile to a mile and a half late just as the Departure Controller queried us. There were no traffic conflicts. We later found a popped computer servo circuit breaker for the center autopilot and we wrote up the malfunction in the logbook. The rest of the flight was uneventful.