Wiring AC power supply - polarity


Old 07-07-14, 01:20 AM
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Join Date: Jul 2014
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Wiring AC power supply - polarity

Hi all,

I recently bought a second hand Midiverb 3 effects unit without a power supply. I had a 9vAC output powersupply as required but with the incorrect barrel size on the end to fit the unit.
I purchased the correct size power connector, cut the old one off the supply and connected the wires.
However there doesn't appear to be any clear indicator on either the barrel or the supply as to their polarity (the supply has lines on one side and writing on the other with no diagram either).

Anyway, the first way round I tried the wires everything appeared to work fine.
I then tried it the other way some time later and it also appeared to work fine, except that the LED on the Midiverb 3 that indicates the presence of a signal was not lighting up as it did the first way round.
So I then switched it back the otherway, again it appears to work fine but the LED isn't lighting up anymore.
I should note that this unit is old and the last two times trying it were through a different wall socket, and I didn't try for very long these times as I didn't want to damage it.

TLDR: does the order of wires for an AC output power supply matter when connecting to a new barrel connector?

Thanks in advance for any help / ideas
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Old 07-07-14, 04:30 AM
chandler's Avatar
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Join Date: Dec 2005
Location: USA
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Welcome to the forums! What part of "non-USA" do you live in? If you had to change the barrel on the end, your amperage rating on the power supply is incorrect for the unit. What amoerage does it require, and how much did you allow it to have?

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