Re: Boss pedals... changing power supply type?
The *old* boss pedals used the old ACA-120 adaptors, they were around 12VDC to 13VDC, the internal pedals used a resistor to knock down the voltage to what the pedals wanted ... an HM-2 though is not *old* per se', but was designed to run off the ACA series ... problem >>>>
The modern ACA-120 are 9 VDC (300mA max. current draw), the PSA-120s are 9.6VDC (200mA max. current draw), and are regulated.
So they are basically the same as the PSA series, the thing is if you use a pSA with an older pedal that was *designed* for receiving 12~13V at the adaptor jack, then the led will be dim (quick test, plug a PSA into an ACA pedal ... if the led is dim, you need to mod the pedal).
I don't know what models are actually expecting the higher voltage (in the ACA series), and which ones are expecting the *newer 9VDC ACAs*, Not sure whan they changed them over either.
There is a resistor in the ac adpator jacks path, you take a piece of wire and bypass that resistor to make the pedal take the (9.6VDC of the PSAs, or (VDC of the new ACAs) correct voltage. That pedal can *never* be hooked to the old ACA series again (as it won't knock the voltage down to ~9VDC).
The HM-2 only draws 10mA @ 9VDC, you must make sure the polarity is correct though on the barrel connector, the boss has protection circuitry against reverse polarity, but you can still blow it by using an adpator that has the opposite polarity. ... The boss is center negative (the pin), and positive outer (the sleeve). When in doubt, measure it.