I have an older Omina that’s been in a drawer for a while. It stopped working a while back, possibly after being hit with a higher voltage that it should (48v PoE power supply possibly). No blinky lights at all with any appropriate 12v power supply. No obvious scorch marks on the board. I looked at it again & saw a removable component next to the power socket. When I pull it out I get an open circuit with the multi-meter. I’m assuming it’s a fuse, hopefully just a blown fuse & nothing else.
Dug up https://wiki.turris.cz/_media/rtrom01-schema.pdf. Poked between COTP121 & ground. Get about 12v when the fuse is out, but less than 3v when I put the fuse in. Weird low ohm readings between positive & ground poking at things with the multimeter when nothing is plugged in. Looks like something in deeper is shorted out. I’m up against my electronics debugging limits. I may be able to resolder a smd component or 2 if I could find the failure point, but probably gonna toss it back in the closet.
Use your meter, set it for continuity testing and check the TVS diode located below DC barell. It is black rectangle with white stripe on the left.
Search for D15 or SMBJ12A in the schematics.
Yup that’s the beauty of open source hardware.
I once managed to plug my speaker’s PSU in the Omnia (36V, I think - some Creative T40s). It didn’t die instantly, but it did die quickly.
Pulled up the schematic, figured with the multimeter that the Zener was fried in the input circuit, removed & replaced that (the electrolitic cap too, just to be sure). Everything worked again, and it’s been working just fine since 2020 when this happened.
