What was found
ON APPROACH TO 26L WITH THE LT AUTOPILOT ENGAGED, RECEIVED MULTIPLE FAILURES, INCLUDING EICAS MESSAGES & INDICATIONS: AUTOPILOT FAIL, BLEED ISLN VAL, LT YAW DAMPER, RUDDER RATIO. AMBER REV, LT EPR , DUAL AMBER DCU ON CAPT PFD & ND STBY ATTITUDE (EFI) FAILED. ADDITIONAL STATUS MESSAGES INCLUDED, FLAP/SLAT ELEC, WARN ELEX, & FLAP ISLN VALVE. CONTROL WHEEL TRIM SWITCHES INOPERATIVE IAW MDIS 24-50/4243. AC STBY PWR WORKING, BUT NO DC STBY PWR. T/S IAW WDM 24-54-73. CHKD 28VDC AT C/B DC STBY BUS OFF, CHKD OK. CHKD 28 VDC AT C/B CAT III BUS ISOL BAT, CHKD OK. CHKD 28VDC AT C/B CSEU 1L, CHKD OK. CHKD 28 VDC AT C/B CSEU 2L, FOUND NO 28VDC & C/B SCREW AT CONNECTER B LOOSE, MAKING NO CONTACT FOR ALL OTHER ELECTRICAL STRIPS OF DC STBY PWR . TIGHTENED SCREW IAW SWPM. PERFORMED ELEC STBY PWR IAW AMM 24-33-01-4 , NO FAULTS. A/C OK TO CONTINUE.