Aesthetix Io won't start...

One thought: some of the Io units have fuses mounted on the circuit board inside the case. Later production units eliminated these, but my unit has them. If you're comfortable opening the case, do so and take a look for a typical BUSS style fuse (glass with metal end caps) mounted on the circuit board and check that fuse. Jim now manufactures the Io with this fuse bypassed and inoperable because it tripped to easily and proved not to add any real value in protecting the circuit. I had this fuse trip on me once several years ago and Jim had to tell me about it's existence. I replaced it and have not had another problem.
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Great advice, many thanks Rushton. My power supply has two fuses in the back and two mounted on the board itself, one of them says Buss MDL 3/8. This may be broken, has some black dots on the inside of the glass even if the thread looks whole. I have not found any fuses on the main unit motherboard (this is mk2). Will get new fuses and report back.

Problem solved, thanks to Rushton's advice! It was the Buss fuse that was gone. Great to get help like this.