What was found
AIR TURNBACK ON DEPARTURE THE LANDING GEAR HANDLE WOULD ONLY MOVE TO THE UNLOCK POSITION. GEAR WOULD NOT RETRACT. WE RAN THE CHECKLIST AND PUT THE GEAR BACK IN THE DOWN POSITION. NO OTHER INDICATIONS THE #1 PITCH TRIM PADDLE ALSO KICKED OFF. WOULD NOTFOUND C/B 2GB-L/G PROX DET & RELAY SYS 1-BREAKER POPPED. SHORT TO GROUND OCCURING SOMEWHERE IN 104VU CENTER RELAY BOX. REMOVED ALL ASSOCIATED RELAYS TO TERMINAL BLOCK 158VT AND BREAKER STILL POPS, REQUIRES FURTHER T/S. PERF SHORT TO GROUND TEST REF ESPM 20-52-21 F. PERF LANDING GEAR EXT & RETRACTION IAW AMM 32-31-00-0501. OPS CK GOOD.