So, I went home and jotted down a ToDo-list:
- Move existing cable to different, known functional port. Or validate existing port+cable function.
- Change patchcable
- Check router logs for DHCP IP allocation to MAC ...:A4 (assuming device does use MAC printed on label)
- Replace PSU - just to be sure it's not that;
Failing setup acted like this:
Cable to LAN. Power-up sequence:
repeat
1 lit for 20 sec
1 fastblink for 3 seconds
1 slowblink for 6 sec
forever
No registration on ocp.outages.io
The '20-second LED_1 lit' indicated boot, and the repeating pattern hinted that device fell flat on its face, only to retry. Rebooting could easily mean a software-issue. I work with embedded software, and can vouch for that!
Anyways, working through the list i got all the way down to "Replace PSU" without finding anything.
Existing PSU was a 1A-capable Apple charger, chosen because of its reputable origin.
Switching to another power source (the router's USB-port) fixed the issue. Just like that...
D'oh!
I've checked the Apple charger, and it delivers a healthy 5V at 0.4A, way past the requirement of the Yellow Mango-router. Puzzling... Maybe the charger can no longer maintain voltage with current fluctuations, causing the Mango's CPU to BOR. Dunno.
The takeaway from this is to avoid assuming things when debugging.
Case closed. Thank you for sparring with me.