First off, let's just state I'm an idiot. OK, done. I've only made it sequentially to page 60 of this thread, but did a lot of targeted searches in the hopes of finding a solution.
Got an ICX6450-24p from ebay, everything was working great... except a slight fan whine. So, before ordering some of the recommended sunon or noctura fans, I figured I'd tried to see if the switch could run fanless or with the case off.
First, I disconnected both fans with cover off. Seems to run fine with ambient temps for 30 minutes, never even reaching the warning threshold.
So..... next, I covered it back up. Turned on and figured let it cook for a bit, assuming the critical shutdown would protect the switch. Well, I went about and did chores and like 15 minutes later came back to a dead switch.
Dead switch = no lights, no fans. Only a slight relay click/pop near power supply when applying power. Kill-a-watt shows 9 watts. Serial connection shows nothing.
Left it to cool down without power, nothing.
Left it to cool down with power, nothing. Google-fu seems to imply there's a 5 minute restart timer if/when temperature hits critical.
So, now trying to troubleshoot: If I disconnect the 14-pin power connector to intermediate/EPS board, no click when applying power. If I disconnect the 10-pin power from intermediate/EPS to mainboard, no click when applying power. Assuming the board is like a PC power supply, there's a "power button" switch that triggers the click when I apply power. Tried holding down the front reset button for 30+ seconds with and without applying power.
Most likely I fried the mainboard and/or the power supply. Tried removing the POE board/power cables too.
So my last hope for now, is that perhaps there's a jumper, fuse or something physical not letting the power supply (assuming it is working) apply power to the mainboard (led/fans/cpu/ram) because of an overheat event or perhaps broken temp sensor. Already ordered another icx6450-24p, so can at least check power supply swap and see what happens when that arrives.
Also if anyone has diagrams and suggestions on what to test on the plugs with a meter, that would be great! My googlefu hasn't been good at finding info on their proprietary stuff.
ebay for just icx6450-24p replacement power supply comes up empty, but the ICX6400 external power supplies seems like a way to "fix" this, although most items cost almost as much as another switch anyways lol. So if anyone has experience with the ICX6400 EPS being the main/only power supply with a presumably working mainboard, that'd be reassuring to hear.
Editted to add: no obvious burn marks, no burning/burnt smell.