AN EMB145 HAD 4 DEFERRED ITEMS: EICAS 115 VAC WARNING; TCASII; EGPWS AND ACARS PRINTER ALL INOP. FOUND ACARS PRINTER SHORTED CAUSING ALL FAULTS.

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ON ACFT X; FLEW INTO XXX FOR OVERNIGHT MAINT. THERE WERE 4 MEL'S AGAINST THE ACFT -- ALL RELOCATED TO THE 115 VAC SYS: 1) MEL #24-03115 VAC BUS OFF MESSAGE ON EICAS. 2) MEL #34-33 TCASII INOP DUE TO MEL #24-03. 3) MEL #34-20 EGPWS INOP DUE TO MEL #24-03. 4) #23-06 ACARS PRINTER INOP DUE TO MEL #24-03. DURING TROUBLESHOOTING; I FOUND THAT THE 115 VAC INVERTER WORKED PWRING ALL THESE SYS FOR 10-15 MINS AND THEN 115 VAC BUS OFF MESSAGE WOULD APPEAR ON THE EICAS; ALL ITEMS MEL'ED WOULD FAIL AND AN ELECTRICAL BURN SMELL WOULD BE EMITTED FROM THE ACARS PRINTER. I FOUND THAT IF I DISCONNECTED THE ACARS PRINTER CONNECTOR; THE 115 VAC BUS WOULD STAY ON-LINE AND THE TCASII AND EGPWS/WINDSHEAR SYS REMAINED OP; BUT WHEN THE ACARS PRINTER WAS RECONNECTED; IT WOULD FAIL AGAIN. MEL'S #24-03 AND #24-20 WERE BOTH CAT 'A' MEL'S GNDING ON XXX; MEL #34-33 IS A CAT 'B' AND GNDED ON YYY; MEL #23-06 GNDED ON ZZZ. I REPLACED THE 115 VAC INVERTER NOT KNOWING IF THE ACARS PRINTER MIGHT HAVE DAMAGED IT. DID NOT HAVE A PRINTER IN STOCK. I DISCONNECTED THE ACARS PRINTER CONNECTOR; COVERED IT WITH A PLASTIC BAG AND SECURED IT OUT OF THE WAY IN THE PEDESTAL. THIS WOULD ALLOW THE ACFT TO FLY UNTIL A PRINTER WAS AVAILABLE. IT WAS ALREADY MEL'ED AND COULD OPERATE FOR ANOTHER 7 DAYS WITHOUT CAUSING PROBS WITH THE 115 VAC BUS; TCASII; AND EGPWS/WINDSHEAR SYS.