Replacing the battery requires a battery holder to be fitted unless you can find an exact replacement. Nasty job for someone in a hurry without the right parts to hand. The board has to be completely disconnected to make sure you don't stress the mini molex connectors. I normally take all the panels off and tighten the pots and sockets while I'm visiting. Also worth checking the solder connections to the power in socket and the jacks, they take a direct hit when the unit slides off the top of the handle on your Mesa Boogie. I use a solid sleeved wire to convert the holder to have pins which align with the holes in the board. I've done a few, and you have to reset the device after. The lack of contrast is a give-away. I failed to find the reset code immediately, but I tried the typical 2 or 3 button press sequences. Holding the BYPASS and EXIT buttons while powering up erases all the user memory, andf everything looks normal, saves to user memory etc. Could be wrong, mine wasn't previously scrambled, but I'm 99% sure that's it. Then you need a dump of the presets you took before the machine got too flaky. When new they have a duplicate factory set, which I duped by copying all the P patches into the U patches one by one, good for testing the dump restore process which can be tedious over the changing platforms over the years. I've used Sounddiver mostly, but Cakewalk 3.0 did it with sysx fine, although you can't see if the memory is worth anything until you reload it in a machine. My two MP5's got new backlights for Christmas, they fade quickly when you leave them on for years at a time. MIDI-rakete.de had them, and lots of others. Good service, decent prices