MikroTik router ethernet repair - Page 1
Forum section: electronics / repair

author: janegil
author_rank: Newbie
timestamp: December 24, 2019, 10:19:12 am
content: Hi!I've got a MikroTik CCR1036-8G-2S+ that was hit by lightning. Knocked one of the ethernet ports out. I have replaced the physical ethernet port, since the internal transformer circuit was toast.I need help identifying a diode that also needs replacement. The diode is in line with the RX and TX connecting the ethernet port with the Atheros AR8033 ethernet controller.As far as I can tell, the diode reads "AF 17". Thanks in advance.

author: wraper
author_rank: Unknown
timestamp: December 25, 2019, 12:58:54 am
content: You don't necessarily need exactly the same ESD protection device. Other low capacitance part with the same package and pinout will work just fine. Looks similar to thesehttps://www.arrow.com/en/products/sp1004u-ulc-04utg/littelfusehttps://eu.mouser.com/ProductDetail/Nexperia/PUSB3F97X?qs=sGAEpiMZZMvxHShE6Whpu07rV54dNgxeHLUrPCoLuS4%3D

author: TheMG
author_rank: Frequent Contributor
timestamp: December 25, 2019, 01:23:42 am
content: This might be the one. At least, it's the only one I could find on Digikey with a package marking that fits (starts with an A, has a letter as the second character, and two digits).http://aosmd.com/res/data_sheets/AOZ8808DI-05.pdfIt should work fine even if it's not the exact same part. It's a TVS diode array for ESD and surge protection. Datasheet above mentions that this part is suitable for ethernet port protection among other uses.

author: janegil
author_rank: Newbie
timestamp: December 25, 2019, 12:15:59 pm
content: Wow, honestly, thank you so much!I'm getting about 0.39V drop between pin 1 and ground for the working diodes on the PCB, would all of the above linked products work?

author: wraper
author_rank: Unknown
timestamp: December 25, 2019, 12:50:53 pm
content: Quote from: janegil on December 25, 2019, 12:15:59 pmMeasure dimensions of the part. Also it would be useful to see actual pads underneath after desoldering component. Also without ESD suppressor present, port should work. If it does not, most likely one of AR8033 is damaged.

author: janegil
author_rank: Newbie
timestamp: December 26, 2019, 11:36:00 am
content: Physical dimensions match. Will test the port after removing the ESD suppressors. I have also ordered a couple of AR8033 in case I need to replace that as well.Btw, the router thinks there is a cable connected to the port, would the shorted diodes be responsible for this behaviour?

author: magic
author_rank: Super Contributor
timestamp: December 26, 2019, 06:05:49 pm
content: Kinda doubt it, the IC may be blown. What speed/duplex is reported?

author: janegil
author_rank: Newbie
timestamp: December 26, 2019, 07:30:20 pm
content: Quote from: magic on December 26, 2019, 06:05:49 pmIt reports 1Gbps full duplex. Also, the yellow light on the ethernet port is on.

author: magic
author_rank: Super Contributor
timestamp: December 27, 2019, 01:39:42 pm
content: That requires some negotiation to establish the link, doesn't it? I think the chip is blown and reports link erroneously.It actually is possible for a gigabit NIC to establish link with itself, but it requires four different wires to be correctly looped back to another four wires. Highly unlikely to occur by random fusing of ESD diodes, but I have built a cable which does that.editNope, my cable only achieves 100Mb/s by pretending to be a two lane crossover cable. My NIC fails to sync up at 1G with it.