[sdiy] Converting rack mount to DC input?

[Mike Beauchamp]

Hi Mattias,

If the 16 V AC is going into a standard rectified bipolar supply, one 
side of the AC line in each of those two units is being tied to ground.

In your case, I'd guess that each device ties a different side of the AC 
line to ground.

Here's the schematic for a really similar power supply:

https://musicfromouterspace.com/analogsynth_new/WALLWARTSUPPLY/wallwart_added_load_rs_schem.pdf


If you modify your Y cable to swap the AC lines on one of the outputs, 
it will probably work again.


Mike





On 2026-07-04 17:19, Mattias Rickardsson wrote:

> This reminds me of a somewhat similar issue I had many years ago:
> 
> I wanted a Korg MS-20 and a Korg KR-55 to share one external power puck. 
> (Swedish-sold old Korgs had a big external power transformer to step 
> down from 220 V AC to 16 V AC, which is then what the instrument then 
> accepts via a plug with 2 flat prongs that doesn't seem roadworthy with 
> European electrical standards.)
> 
> So I made a short splitter Y cable on the 16 V AC side and attached both 
> instruments and turned them on. But then I connected an audio cable 
> between them (or audio cables from both units to the same mixer) and I 
> had a blown fuse! It was apparently not okay to connect those two 
> grounds together when running off the same AC supply.
> 
> /mr
> 
> 
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