JamMan Stereo Bootup Problems? Fix HERE
Try this if you are having JamMan frozen bootup problems (requires an SD Card)
"Upon booting the pedal, does the pedal ever display firmware version? It should show “JS” then “1.X” version number. If it does not display a firmware version, perhaps attempt to reload the firmware manually using the files linked below. You will need to unzip the .zip folder’s contents onto the root directory of an SD card. The SD card will be put into the Jamman with power turned off. Powering on the Jamman, the pedal should automatically check the SD card first, then attempt to load the new firmware. If the pedal successfully boots, remove the SD card and do not put it back in the pedal until you remove the remaining update files from the card. Let me know what you find."