Mototrbo repeater defective power supply

[olan]

hi guys,

my repeater power supply got busted, the fuse, busted. replace it with the spare
but still it wont turn ON. install a backup power supply plug it on the rear
battery back up socket, it works. question, if i remove the built-in power
supply, for purpose of repair, how can i power it up using a back up power
supply? help needed. thanks!

olan