Hello, My T42/2379 will only run on battery power. When a/c adapter is plugged in the unit will immediately go black screen and standby. As soon as adapter is removed from jack,display returns and functions normally. Any help would be greatly appreciated.

Most likely your charger is damaged, or the yellow DC connector on the back is loose and somehow shorts when you plug it in.
Buy/borrow another IBM adapter (16V/4.5A/72W), don't try a generic one.

Thanks for the quick reply. Found a relatively inexpensive unit on ebay as well as a dc jack to hopefully cover all the obvious causes. Would it be unusual for my current charger to only cause a problem when lid is open but to charge battery normally with lid shut? Thanks.

Update to stubborn issue with t42/2379.
As previously stated, my T42 will only run on battery power. As suggested I have replaced the charger/adapter, d.c in jack,and after no success with those repairs I also replaced the inverter board. The inverter board seemed to do the trick but after a day of use the problem resumed. Any help would be greatly appreciated. I'm becoming more and more determined to fix this unit with all the time that has already been invested.

P.S As I type, the computer which has been plugged in,black screen for several hours and sitting undisturbed on a work table across the room has started to flash off an on for a few seconds at a time in a random manner. ??????? taunting me!!!