noise: Need help building PSU for 1980's drum machine

Johny Radio johnyradio at
Thu Nov 21 20:39:40 UTC 2013

On 11/21/2013 10:56 AM, James Sundquist wrote:
> The powersupply is proprietary and only available on eBay, but I've read


here are some simple ways to get a dual power supply.

this article gives the best, understandable explanation and walkthrough 
of the simplest methods to get a dual supply. You can use two batteries 
(or two wall warts) and two caps (or even just one battery or wall wart 
with resistors). But as the batteries drain unevenly, they will become 
unbalanced (ie your negative voltage will drift from your positive 
voltage). For your needs, might be fine! Worth a try. they also provide 
simple improvements to fix that problem:

another example using just one battery or wall wart. Read notes under 
the pic:

in a pinch, you could also just try two batteries and nothing else. 
Connect the plus of one battery to the minus of the other battery-- that 
point becomes your ground common 0 volts.

two wall warts: i powered a 60 watt power-amplifier with two wall warts 
and nothing else. Worth a try, it's the easiest way i found to get a 
dual power supply. Find two identical wall warts; from a laptop computer 
will give you more current (but more current maybe not necessary for 
your drum machine). Make sure they output enough amps (see what amps 
your drum machine needs, maybe on a label on the back of the machine). 
Connect the left output lead of one wart to the right output lead of the 
other wart, and that becomes your 0V (ground). The other leads are your 
plus and minus. Then plug both warts into a wall and check outputs with 
a voltmeter.

last, you could build a proper supply. here's one using only 
transistors, no chips (note 4 diode bridge rectifier not shown 
explicitly is needed at input):

This one uses regulator chips. You'll have to find or order the chips:

Johny Radio

Stick It In Your Ear!

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