"A friend is loaning me a Moog Etherwave that her gf's Dad built from a kit years ago, but it's missing the power cable. It's the 5-pin DIN connector, and from what I'm seeing online, they're pretty hard to come by? Someone suggested to DIY it & solder a connector to a new power supply, but... I need more instructions. I'd love some leads on vendors that might have it, or a how-to on putting something together that will work (and like, not burn up my friends' instrument!). Any leads would be appreciated!! (I'm in US.)" - spacefaerie
A quick look on the web shows they're all out of stock, even Zzounds which the Moog web site points you to.
The supply itself is pretty simple - I'm showing the regulators and associated passives here too, which are internal to the Etherwave and not the supply, which is just a transformer:
If I were doing this I'd buy a raw 115VAC / 14VAC transformer and stick it in a plastic project box. That would allow me to connect the AC ground to pins 2 & 3 of the DIN, thus grounding the Etherwave (proper grounding is critical to Theremins) - I might include a ground lift switch to eliminate ground loops if the audio path is grounded. I'd maybe include an on/off switch, and perhaps an LED indicator. I would use an IEC socket for the AC input so I could pick from the variety of unused computer type cords one tends to collect.
Here is a transformer at Mouser that would probably work: https://mou.sr/4dChZ8p More amperage than 200mA is OK, less isn't.