Several years ago, my buddy Alex and I bought a couple Vox DA5 battery-powered amps for use while busking and for other portable-amplification purposes. The "baby" Vox's most recent adventure was while we were on tour with The West Nile Ramblers in Ireland last summer. 

Unfortunately, either on or before that trans-Atlantic voyage, my amp stopped working on battery-power. It still functioned using the AC/DC wall wart, but that made it considerably less handy to use. I managed to forget about this after returning from Ireland and brought it out to California in April only to find out (again) that it didn't work with batteries alone. Whoops.

After checking to make sure that the batteries were making contact in the battery pack, my next step was to crack open the amp to see if I could figure out what was going on. As is typical with a lot of modern consumer electronics, this thing was not built to be user-serviceable. The circuit board was not easily accessible and I didn't want to mess around with it too much lest I cause the amp to stop working completely. I reassembled the amp and got to thinking...

Then it hit me - since the amp still worked using the AC/DC converter, I just needed to rig up the battery pack to plug into the same spot on the back. A quick trip to RadioShack, $20, and some soldering later, I once again have a functioning battery-powered amp!