OK, here goes.
Creating a Magnetic Battery Compartment Door for a Sire M5 Bass:
1) Remove the four wood screws that attach the battery compartment lid (door) to the body.
2) Snip/saw/grind the wood screws until only a thread or two remains beneath the screw head.
(Note: The amount of screw length you leave beneath the screw head will vary with the amount of 3mm diameter magnets in the stack you will use in a future step. More on this later.)
3) Measure the depth of a screw hole by sticking a toothpick or something similar in it. Make a note of the depth because you will use it to determine how many 1.5mm you will need to stack up to fill the hole at the proper depth.
(Note: You will NOT fill the hole to to be flush with the hole surface! You must leave room for the depth of the 3mm diameter "cap" magnet! More to come.)
4) Stack as many 1.5mm diameter magnets as will snuggly fit down each of the four wood screw holes in the bass body.
(Note: This number will vary depending on the depth of each 1.5mm magnet you use.)
5) Tap the stack of 1.5mm magnets down into each screw hole with a small punch or finishing nail set so each stack sits recessed in the hole.
IMPORTANT: Tap the magnet stack down so it leaves about 2mm of depth from the surface of the hole so a 3mm "cap" magnet that will sit atop each 1.5mm magnet stack will be able to sit flush with the screw hole surface.
6) Enlarge each body screw hole to accommodate the width of a 3mm diameter magnet that will sit atop the stack of smaller magnets.
7) Place and glue the 3mm cap magnet in each screw hole, atop the stack of smaller magnets.
(Note: The resulting, cumulative magnetic pull of the magnet stack and cap is strong.)
8) Door Magnets Installation: Enlarge each screw hole in the battery compartment door to accommodate the width of a 3mm diameter magnet.
9) Place and glue a 3mm magnet in each of the four holes in the door.
IMPORTANT: BEFORE GLUING EACH 3MM MAGNET IN PLACE, MAKE SURE TO ORIENT THE IT IN THE DOOR SO IT IS ATTRACTED TO THE MAGNET IT FACES IN THE BODY.
10) Align the door magnet caps above the battery compartment magnet caps and lower the door to the battery compartment, et voilà!
The four magnet caps in the body and the magnet caps in the door will attract each other and hold the door securely to the bass body.
THE TEST: Hold the bass in your hands horizontally, with the strings facing up. Shake the living crap out of the bass as hard as humanly possible.
THE RESULT: The combined weight of the two 9-volt batteries and the door itself are insufficient to move the door and make it fall open.
WHAT THIS MEANS: The solution works!
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HOW TO REMOVE THE DOOR: Just slip a fingernail near the edge of any door corner and lift the door up slightly to disengage the magnetic pull. Then just lift the door off the bass.
HOW TO REINSTALL THE DOOR: To reinstall the door, align door with the battery compartment, making sure the Sire brand is rightside-up in the proper, legible orientation, and bring the door near the battery compartment. Then rejoice in hearing the satisfying "snap" as the door falls securely in place.
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BIG TIME CAVEAT: Make damn sure all magnets are stacked and oriented so their polarities match!
Just test a stack of them, including the cap magnets, to ensure they attract versus repel each other, then make note of how they need to face each other in order to attract.
Might sound obvious and dumb to call this out, but it is what it is: Test magnet polarity BEFORE inserting the 1.5mm magnets in the screw holes; test magnet polarity attraction of the 3mm cap magnets BEFORE gluing them to each stack: test magnet polarity attraction of each of 3mm magnets in the door BEFORE placing and gluing them down.
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Follow these steps and evermore enjoy quick and easy battery swaps with your spiffy, magnetically-modded Sire M5!
