I recently acquired a (used, of course) Zoom MRT-3B drum machine, a cute little beatmaker from the early aughties (2003, best I can tell). I noticed after playing with it a few times that it was losing all user content every time I turned it off and on, displaying “Init” on startup. Turns out this is not because it’s Bri’ish, but is short for “initialize” which means, in effect, it’s erasing all user content. Bummer.
It occurred to me that this probably comes down to it storing user settings in battery-backed ram, and said battery was probably extinguished at 21 years of age. So I set about finding and replacing the battery in question. Sadly, I didn’t think to blog this for posterity until all was said and done, so I have no pictures for this tutorial. Nevertheless, hopefully it helps someone restore their machine to full use.
Before you tackle this job, here’s what you’ll need:
- A phillips screwdriver
- A soldering iron and some solder
- A solder sucker or solder braid
- A CR2032 battery (the quarter-sized coin battery you can find pretty easily)
- A CR2032 battery holder
- A clean workbench and something to hold the bits and bobs you take out.
- Possibly a spoon. Or whatever you prefer to use to remove knobs.
Got all that? Good. Give yourself 30-60 minutes depending on your skill level and let’s get at it.
First thing is that you’ll need to remove every last screw out of this thing. That includes the back panel (4 black screws), MIDI port (two small black screws), battery holder (4 black screws), Top circuit board (2 silver screws — mind the little wires that ground the back panel), and bottom circuit board (like 5 or 6 silver screws — can’t quite remember now). You’ll also need to remove the volume knob to get the top circuit board off. Mine was a bit stuck, I just carefully pried it off with a teaspoon. Be gentle, the pot shaft is plastic.
Once you have the back panel, battery holder, MIDI port, and top circuit board unscrewed, you’ll have to remove the top board to get to the screws on the bottom board. Carefully wiggle it out, it’s kind of tricky because the power switch requires you to back it out while the USB port bumps against a screw post. You can do it, though, I believe in you. Note that there’s a ribbon cable connecting the two boards on the left side, so be careful not to jostle it to roughly.
Now, if you’ve got all the screws out of the bottom board, carefully lift out the board and flip it over. Keep the case face-down so the buttons stay put, and try to avoid any loose debris falling down on the buttons. You’ll see a coin battery spot-welded onto a couple of battery clips. Good luck undoing that.
Do yourself and posterity a favor and flip the board back over and desolder the battery clips. I had my iron at 750°F and the solder on this melted readily. Install the new clip, taking care to position the positive and negative poles as marked. My clip was about twice the height of their welded battery clips, but it fit fine. Didn’t stick up any taller than some of the caps on the board, so don’t be too worried about height.
That done, I dropped in a fresh (and TESTED) CR2032 and started putting everything back together. Don’t forget to install the Earth wire that attaches to the silver screws on the right of each board, and don’t forget the top board’s little wires on the two silver screws that stick up to ground the back panel. They should be angle-upward with the ends pointing down into empty space.
Once I’d got it back together I dropped in some fresh AA batteries and we’re off to work. User settings saving just fine now.
As a final note, Zoom engineers of 2003: WHAT THE EVEN HECK? I get saving money, but did you really never anticipate people wanting to use unit this beyond the lifespan of a CR2032? Would it have killed the cost of this unit to put a battery clip in an easily accessible location? Surely we knew even as far back as 2003 that musicians love old gear, that styles are cyclical, and that someone might actually enjoy using this unit in the distant flying-car space age of 2024? I hope in the intervening two decades we’ve moved beyond this sad design (maybe I need to take apart my B1XFour and find out?)
As for you, reader: Hope this helped you!
