What was found
DURING CRUISE AT FL290 AND WITH APU OFF, CREW REPORTED YAW DAMPER NR 2 AND AUTOPILOT WENT OFF AND EFIS COMPUTER MONITOR MESSAGE AND HDG AND PIT BOXES DISPLAYED. F/O SIDE PRIMARY FLIGHT DISPLAY (PFD) FLICKERED WITH VERTICAL BARS. ATTITUDE INDICATOR CLIMBING, HEADING AND COURSE WAY OFF AND YAW DAMPER WOULD NOT RE-ENGAGE. CREW RAN QRH. AFTER APPROXIMATELY 10 MINUTES, MOST INDICATIONS CLEARED THEMSELVES. CREW DECLARED EMERGENCY AND LANDED SAFELY AT DESTINATION. MAINTENANCE TROUBLESHOT, R & R ATTITUDE HEADING COMPUTER NR 2 AND PERFORMED CHECKS IAW AMM. ACFT RELEASED FOR SERVICE.