This is a Music Easel I had for repair. That's a suitcase type case with a 218 touchplate keyboard, a 208 stored programmable sound source and a 214/215 power supply. The power supply was not working on this unit. It was designed to be operable from 12 volts in batteries as well as from the wall AC. It takes the 117 VAC and sends it through a huge 12 volt transformer. This 12 volts is filtered with a GIANT capacitor. Then that unregulated 12 volts is plugged in where a battery would have also worked. There's a circuit that takes the 12 volts in and spits out +/-24 volts. That is then regulated down to +/-15 and +5 by the normal 215 power supply card. I have cloned that "voltage booster" card and I think I'll use it in my 203 cabinet if I ever need to power a 24 volt module. By the time Don made the 203 cabinets, he had stopped using 24 volts in his designs. Those cabs have Power One brand single output supplies accross the back. Mine is 8 spaces wide so it has doubles of the positive and negative 15 volt supplies. The top two boats get their own.