What was found
CLIMBING THROUGH FL250, CREW HEARD A LOUD THUMP FOLLOWED BY A LANDING GEAR UNLOCK LIGHT INDICATION. DURING DESCENT THROUGH 4000 FT, HEARD A THUMP FOLLOWED BY THE “UNLOCK” LIGHT GOING OUT. FOLLOWED CHECKLIST TO LOWER AND BLOW DOWN GEARS, HAD NORMAL GEAR INDICATIONS 3 GREEN AND NO RED, AIRCRAFT LANDED WITHOUT INCIDENTS. TROUBLESHOT GEAR SYSTEM AND FOUND EMERGENCY GEAR UP-LOCK RELEASE CABLE TENSION TOO TIGHT. RE-RIGGED UP-LOCK EMERGENCY GEAR CABLE TENSIONS AND PERFORMED EMERGENCY GEAR UP-LOCK RELEASE IAW CESSNA 750 MM CHAPTER 32-30-05 FOR MAIN GEAR AND 33-70-06 FOR NOSE GEAR. SERVICED PNEUMATIC BOTTLE IAW CESSNA 750 MM CHAPTER 12-19-36, OPERATIONAL CHECKED GOOD.