What was found
PDX- ON TAKE OFF WHEN GEAR SELECTED UP NOSE GEAR DID NOT IMMEDIATELY RETRACT (ESTIMATED 30 SECONDS). RED AND ORANGE LIGHTS REMAINED ILLUMINATED. EVENTUALLY ALL LIGHTS WENT OUT BUT AFTER A BRIEF DELAY RED AND ORANGE LIGHTS CAME BACK ON AND WIND NOISE WAS HEARD AGAIN. ALL LIGHTS EVENTUALLY EXTINGUISHED. GEAR FAILS TO RETRACT, CHECKLIST MADE SURE THAT ALT GEAR DOORS WERE CLOSED. WHICH THEY WERE.LANDED WITHOUT INCIDENT. REMOVED AND REPLACED NOSE LANDING GEAR MECHANICAL SEQUENCE VALVE. OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE.