A BE1900D ON LEVELOFF AT 17000 FT HAD MASTER CAUTION WARNING ILLUMINATED. CABIN PRESSURIZED TO 12000 FT. BEGAN TO GET MULTIPLE SYS FAILURES.

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SHORTLY AFTER LEVELOFF AT 17000 FT; MASTER WARNING ILLUMINATION CABIN ALT. CREW FOLLOWED APPROPRIATE CHKLIST. CABIN ALT MAINTAINED APPROX 12000 FT. CONTINUATION OF FLT UNDER FAR PART 91 FOR REPOS. FO NOTICED #2 DME NOT WORKING/INDICATING. WE TRIED OTHER FREQS WITH NO CHANGE IN DME STATUS (INOP). SHORTLY AFTER THAT (10 MINS); AC BUS ILLUMINATION. FOLLOWED CHKLIST AND XFERRED TO #2 INVERTER. MOMENTS LATER; CAPT DPU FAILURE. FOLLOWED CHKLIST XFER TO ALL DPU #2. NOW NO DME INDICATIONS. UPON LNDG IN ZZZ; WE WROTE UP: 1) CAPT CLOCK INOP. 2) L AC BUS/INVERTER L SIDE FAILURE AND INTERMITTENT. 3) L CAPT DPU INTERMITTENT. 4) CABIN DOES NOT HOLD PRESSURE. 5) RATE CONTROLLER APPEARS NOT TO CTL CABIN RATE. 6) FO DME INOP. ALL ITEMS ABOVE WERE INSPECTED AND CLEANED BY MAINT FOR THE FOLLOWING DAY. (THE DME ON FO SIDE WAS DEFERRED.) CREW THE NEXT MORNING TOOK OFF FROM ZZZ. LATER INVESTIGATION DETERMINED THAT MAINT IN ZZZ1 DID NOT INSTALL #2 DME ANTENNA; WHICH RESULTED IN DME FAILURE AND PRESSURIZATION PROB. (ACFT JUST CAME OUT OF STRUCTURAL MAINT.) CAUSE OF PROB: POOR OVERSIGHT BY MAINT PERSONNEL. POOR PASS-DOWN DURING MAINT CREW CHANGE.