Thursday, 20 July 2017

BOSS HM-2 Mod. Make it work on a 9v Power Supply

I recently scored one of the legendary BOSS HM-2 MIT beasts. I got in in an auction on eBay saying it was faulty. The description was along the lines of "works with a battery but not a power supply". I thought hey I know what that is!!



Boss have this ridiculous thing where they made you buy only BOSS power supplies back in the day. They called it ACA. Essentially they set up the pedal to work from a 12v supply by adding a resistor and a diode in series with the supply.
HM-2 Schematic

Here is a close up of the section that I need to do the mod.

I want to keep this as close to original as possible So instead of removing D1 and R2 and putting a link in I will just put a solder blob across wire 4 and wire 5




With the solder blob in place the mighty HM-2 will now run from a 9v supply perfectly. This mod can be applied to any BOSS ACA style pedal. If you are going to do this mod make sure that you confirm the correct components and wires.


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