I just had this problem and wasn't able to find the solution on line, so, here 'tis.
Take off the six screws on top of the amp cabinet. Unplug the speaker plug from the amp jack.The metal amplifer box can now be pushed out of the back of the cabinet and the input jack remounted. I had to force the box a bit as it was glued in just enough to tack it into place. (I was afraid to force the electronics box out so I took the entire cabinet apart piece by piece until I could see there was nothing left holding it in.) I found that prying it this way and that with a butter knife helped crack the glue.
I was looking at how the head is setup not sure if it is the same as the combo. But the amp chassis slides in from the back into the amp box. Probably attached with 2 screws on either side of the amp. Just examine the case carefully.
Answers & Comments
I just had this problem and wasn't able to find the solution on line, so, here 'tis.
Take off the six screws on top of the amp cabinet. Unplug the speaker plug from the amp jack.The metal amplifer box can now be pushed out of the back of the cabinet and the input jack remounted. I had to force the box a bit as it was glued in just enough to tack it into place. (I was afraid to force the electronics box out so I took the entire cabinet apart piece by piece until I could see there was nothing left holding it in.) I found that prying it this way and that with a butter knife helped crack the glue.
I was looking at how the head is setup not sure if it is the same as the combo. But the amp chassis slides in from the back into the amp box. Probably attached with 2 screws on either side of the amp. Just examine the case carefully.