Basic electrical question - please help

A

Adam P

Well-known member
I have a handful of effects units in a "modular" setup that each require their own wall wart power supply. Rather than buy an AC adaptor for each unit, I'd like to use the one AC adaptor that I already have, and connect them all via daisychain (such as the Pedalboard.net GV-8). All the units require the same voltage power supply. I know that the total amps draw cannot exceed the AC adaptor's rating, but I don't know the draw of each unit, as I bought them used without a manual, and it's not indicated on the unit.

Would it stand to reason that I could plug one of the units in with the daisychain cable, and measure the amps on one of the other terminals with a multimeter, and subtract this reading from the total rating of the AC adaptor to find the draw of that particular unit? For example, AC adaptor is rated for 1000mA, I plug in one unit and measure the amps at another terminal and read 900mA, so this means the unit is drawing 100mA? Would this be the way to go about doing this, or is there a flaw in my thinking somewhere? Would there be an easier way to find out the draw of each unit?

Thanks.
 
You should be able to find out current draw on the web somewhere. What units did you get?

I don't think your method will work because

1) The supply doesn't always put out 1000 mA. It only supplies what is asked of it depending on the load of devices you hook to it.

2) A multimeter needs to be in series with a circuit to measure current. Putting it across one terminal will put it parallel to whatever unit is plugged into the other terminal. The meter can't read how much current is flowing through the device.

Take a single supply or daisy chain, cut one of the wires (not one of the terminal extensions if you use a daisychain) , set your meter for current, and complete the circuit by attaching your meter leads to the wire. Then plug the supply in. Start on your meter's 10A range.

I have a "tester" power supply that I put a 1W 1Ohm 5% resistor in series with one of the wires, and read the voltage across the resistor. You can convert straight from millivolts to milliamps.
 
Adam P said:
I have a handful of effects units in a "modular" setup that each require their own wall wart power supply. Rather than buy an AC adaptor for each unit, I'd like to use the one AC adaptor that I already have, and connect them all via daisychain (such as the Pedalboard.net GV-8). All the units require the same voltage power supply. I know that the total amps draw cannot exceed the AC adaptor's rating, but I don't know the draw of each unit, as I bought them used without a manual, and it's not indicated on the unit.

Would it stand to reason that I could plug one of the units in with the daisychain cable, and measure the amps on one of the other terminals with a multimeter, and subtract this reading from the total rating of the AC adaptor to find the draw of that particular unit? For example, AC adaptor is rated for 1000mA, I plug in one unit and measure the amps at another terminal and read 900mA, so this means the unit is drawing 100mA? Would this be the way to go about doing this, or is there a flaw in my thinking somewhere? Would there be an easier way to find out the draw of each unit?

Thanks.
Click to expand...

Yes but I don't think your formula is right. A multimeter will show you the current draw across the pedal, not the current "remaining". And the daisychain cable is wired in parallel, so measuring another plug I don't think will work. You might have to open up a pedal and measure the current across its positive and negative power leads.
 
Cool, thanks guys. I see what you're saying.

The units are some 90s era Vestax delay and reverb units that I picked up dirt cheap, but haven't been able to find a shred of info about them online.
 
Also make sure that the polarity between the inner sleeve and outer sleeve of each plug is the same.
 
Yep, all the units are the same (4 delays, 3 reverbs), so they all have the same polarity. Thanks!
 
sorry to jack this old thread back up but



if im running 7 pedals on a pedal board, 6 of which are boss, one MXR, can i use TWO of those daisy chains? well, i know i can, because i am right now, but will i blow a fuse or something?

ive got one of those V-spot power supplies, which has 5 "ends" that go into the pedals, i then bought a V-spot extension, also with 5, so now i have 9 "ends to use up(taking one away from the original 5 when using the adaptor)

is it bad to have all 7 pedals going into one socket on a power strip?
 
StarvingEyes said:
is it bad to have all 7 pedals going into one socket on a power strip?
Click to expand...

Pedals use a trivial amount of power as far as your house circuits are concerned. The issue is the power supply itself, whether the transformer, rectifier, and regulators can take the load.

All you pedals should be labeled for their current draw, or you should be able to find it in the manual. Add 'em up, and compare with the rating on your power supply.
 
Just to respond to my own ancient thread, I did get one of those daisychains and it works just fine.
 
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