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Ubiquiti UniFi AP AC Lite TVS Diode Replacement

Neye ihtiyacın var

    • The front cover is secured by five tabs.

    • Use the Jimmy to create a gap near a clip and insert a plastic prying tool. Apply moderate pressure to force the clips open.

    • Watch out for alignment tabs that may obstruct your progress. Aim to guide the Jimmy toward the center of the front cover.

    • The TVS diode, marked D6 on the PCB, is located between the antenna and a large IC on the RJ45 port side of the board.

    • It is a 24V uni-directional TVS diode with J leads (SMBJ24A) made by Littlefuse. Note the location of the white bar on the diode, as it indicates its orientation.

    • Use a multimeter or ohmmeter to test whether the diode has shorted. A shorted diode will read less than 1 Ohm in both directions. A working diode will have significantly higher resistance in one direction than the other.

    • If the diode is not shorted, then there may be another issue, and proceeding further may not help resolve the problem with your access point.

    • To desolder the broken diode, apply heat to one side while lifting the diode with tweezers. Repeat on the other side until the diode comes loose.

    • If the solder seems to not want to melt, try using a larger soldering tip to transfer more heat and melt the solder faster.

    • After removing the shorted diode, the access point should power up and function normally. However, omitting this step could result in further damage if an overvoltage event occurs.

    • Before installing the new diode, use a multimeter or ohmmeter to verify that it is functioning correctly. A working TVS diode will exhibit significantly higher resistance in one direction than the other.

    • To install the new diode:

    • Check the orientation marking on the diode to ensure it is positioned correctly, with the bar pointing toward the antenna.

    • Apply flux to the pads and add a thin layer of solder. If solder does not adhere to the pads, you can add it to the underside of the diode pins instead.

    • Hold the new diode in place using tweezers. While applying downward force, apply heat to one pin near the solder until the solder melts and makes a connection. Repeat with the other lead.

    • Verify that the connections are good. There should be continuity between one pin of D6 and a pin in VR3, and between the other pin of D6 and D7.


To reassemble your device, reattach front cover.

23 farklı kişi bu kılavuzu tamamladı.

Yang Zhao

Üyelik tarihi: 11/01/16

833 İtibar

1 Kılavuz yazıldı

20 Yorum

Do you think this problem has something to do with Ubiquiti dropping 24V devices altogether? I’ve read about the firmware problems that make 24V passive + POE switch setups a fire hazard, but do you think think this is a design choice or a fix for a flakey on-device power circuit?

Thanks for publishing this, I’ll give it a dead AP I have.

Maxime Rousseau - Yanıt

Mine broke in exactly the use case warned against here: This kind of failure definitely seems to be linked to the ‘accidental’ 48V activation issue. Unfortunately the device is OOW, but I’ll try to hit up Ubiquiti and see if I can get some good will.

Maxime Rousseau -

Thank you! This fixed my Unifi AC Lite, I plugged it into a PoE switch that fried that diode.

effbees - Yanıt

Hi, can some help identify the corresponding Diode from this Tutorial on the Unifi UAP-AC-HD? Its POE sections is a little bigger. But didn’t find shorted Diodes. POE LED on Switch is on, but AP not powering on. It boots when 5 V are supplied manually, so somethings is wrong on the poe section.

It gets warm around the silver elko / capacity next to the transformator. But that’s all what I was able to figure out.

Maya S. - Yanıt

would be D28 from what I can see above C556

Rob Schepers -

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