Hi All, especially Mikrotik,
I’ve CSS610-8P-2S+IN and really bad thing happened. The switch was powered from grid, 2 cameras were connected and powered from other ports. I put network cable (tested cable, all OK) to port1, other side of the cable was connected to ether2 on hAP AX3. The switch started producing loud buzzing sound, probably overloaded power supply in the switch. I disconnected the cable in about 2 seconds and other 2 cameras I disconnected as well. Hmm, what next? Network was connected via SFP fibre module, no galvanic connection. I checked PoE out state on port1, it has been turned off. I tried to connect small PoE powered camera to port1 and the camera woke up and worked. Strange, the switch provides power even shouldn’t.
Ether2 on hAP AX3 works, but 100 Mbps connection only. Ether2 on hAP is broken, cable test shows shorted pair, no cable connected.
I returned the switch to the seller, they refused to repair it because of overvoltage. I think it’s not true. I’ve Citel surge protection T3, T2, T1 in main flat distributor and another T1 surge protection on UPS. hAP was connected directly to mini PC which is powered from 12V adapter. hAP itself was powered from Mikrotik’s power adapter. All devices were connected to the same grid circuit, UPS, surge protection. No other devices were damaged, just the switch itself (provide PoE out on port1 all time) and hAP has damaged ether2 (one pair shorted). hAP port woked well before this incident.
What do you think, what really happened? I’m not sure if I ever connected something to port1 om the switch` can’t say if port1 was damaged when I bought the switch or not.
Maybe there wasn’t overvoltage on the primary side but on the secondary side.. It’s possible that voltage regulation was lost and DC voltage shoot through the roof.
You can check it by opening the switch and examine power supply. You can put some pictures if you want so we can se what happened.
I don’t think that PSU was overloaded as that switch has 140W poe capacity and cameras draw maybe 10W each max.
Thank you for the reply. I don’t have the switch, I have to pick up it from the seller’s office. I didn’t measure anything, but in the web interface the switch reported about 54V on the “high” voltage output. It’s normal value
My opinion - the switch provided PoE when shouldn’t. When I connected it to hAP, hAP port 2 doesn;t like 54 V between pairs, semiconductor(s) failed and there was (near) short circuit (buzzing sound, LED’s on the switch became darker). Even PSU was overloaded, the switch was unable to cut PoE on port1 because of the switching semiconductor is broken. I don’t think PSU was overloaded by 2 cameras, power comsumption was very low - one camera takes less than 4 W.
I’ll pick up the switch and check.
I’m disapointed by Mikrotik’s approach - when semiconductor, Shottky diode fails, it’s always because of overvoltage, which definitely is not true. Semiconductor can fail for many reasons
It’s very probable that the failure happened in the way you describe: the initial “tickle” sensing misidentified the other end, applied power and the protection couldn’t cut it before the switching transistor was damaged.
Designing these sorts of current/power limiters is tricky, to be mild about it. They have to allow overcurrent for some time to be able to charge capacitors, but still maintain the switching element in SOA and within thermals.
The only good news may be that - at least in other models - Mikrotik uses discrete switches, so it may be quite easy to replace it.
The short seen on the port is indeed the result of the overvoltage. (Some element of the protection circuit is shorted.) This is usually quite easy to “repair”.
I once applied 48V to the 24V antenna, only thing that was busted was bidirectional TVS diode. After I replaced the diode everything was working. Maybe is something simple in your case as well. Hopefully…
What I didn’t mention before - PoE was turned of in the web management interface of the switch. It means no “tickling” or PoE handshaking. I do it always on PoE devices when I connect/disconnect anything from PoE ports. 100% sure
I picked up the switch, returned from distributor with 3 photos - 2 with multimeter measuring Schottky diodes - one OK, one shorted + photo of the board itself taken detail of bottom side of the board, partially burned.
Photos are low quality, printed on BW laser printer, they didn’t provide them in digital forms as jpeg or so.
In short - no new information, shell happened (or the sh* abbreviation means something else? ),
or PoE handshaking. I do it always on PoE devices when I connect/disconnect anything from PoE ports. 100% sure
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