What was found
AFTER COMPLETING THE AFTER TAKEOFF CHECKLIST THE STBY HYD PRESS GUAGE SHOWED 3000 PSI STBY HYD PRESS SWITCH WAS CONFIRMED OFF (OUT), DIVERSION. REMOVED FROM SERVICE. RAN NR 1 ENGINE AND WAS ABLE TO DUPLICATE DISCREPANCY, WHEN ENGINE HYDRAULICS COME ONLINE, STBY HYD PRESS SLOWLY INCREASES. REPLACED PORT MOUNTED CHECK VALVE ON NR 1 HYD MANIFOLD, NO HELP, REF AMM 29-11-71-000/400-801. R & R NR 1 HYD MANIFOLD, REF AMM 29-11-31-000-801. STBY HYD SYS OPERATIONS CHECKS GOOD. LEAKS CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.