Take out the two screws then pry the case open and it will come apart. I don't think it is the switch btw. I think there is something wrong with the voltage sensing of the unit. Mine won't power up on alkelines but will power up on nimh's of slightly lesser voltage, but then says battery low.....

Ask your dealer, the one you bought it from. They may suggest an easy fix or guide you best on how to get it repaired, or at the very least suggest a place near you to have it repaired. If your dealer doesn't know, ask any Zoom dealer for repair info. Meanwhile, I assume you've checked your battery compartment to make sure the terminal connections are not loose (and of course that you've tried new batteries - :) ). Also, check Menu>Battery to see if alkaline or nickel batteries is checked. Finally, try removing your SD card and re-inserting, (even re-formatting the card, perhaps, but trying merely re-inserting first). But make sure any songs/info on the card are backed up first, because you will lose info if re-formatting the card. (For that matter, you could try a new card.)

My Zoom H4 will no longer power up with batteries. (yes even fresh batteries) only works with AC adapter. There was only one possible solution that makes sense and that would be concerning the little switch that disconnects the battery power once external power source is plugged in. I'm sure that I can repair this except, I can't seem to take the darn thing apart to do so. I've removed all visible screws and can't seem to dismantle it. It seems very fragile and I would hate to crack the casing. Does anyone know how to open this thing up?