What was found
"AFTER T/O SELECTED GEAR UP AND HYDRAULIC CAUTION LIGHT ILLUMINATED. COMPLETED MEMORY ITEMS THEN COMPLETED AFTER T/O CHECK. COMPLETED EMERGENCY/NON-NORMAL CHECKLIST HYDRAULIC PROC 2. RETURNED TO TRI. DECLARED EMERGENCY AND RETURNED TO GATE. FLAPS REMAINED ZERO. REMOVED AND REPLACED LT PDU IAW SAAB AMM 24-31-20. OPS CHECK GOOD AT THIS TIME, P/N ON AND OFF A2042C, S/N ON CL-86429, S/N OFF CG-81553. REMOVED AND REPLACED RELAY 7ML IAW SAAB AMM 20-20-00 OPS CHECK GOOD, P/N ON AND OFF MS24142D1.