What was found
PDX - FLT 561 - ON ARRIVAL, THE CREW REPORTED THE LANDING GEAR DID NOT EXTEND DURING APPROACH, ALL GEAR POSITION LIGHTS WERE RED AND GEAR WARNING HORN ON. ACCOMPLISHED GO-AROUND AND LANDING GEAR EXTENDED NORMALLY ON SECOND APPROACH. REPLACED THE LANDING GEAR CONTROL VALVE AND ACCOMPLISHED GEAR SWING, LANDING GEAR OPERATED NORMALLY. (W)