Ubiquiti UniFi AP AC Lite TVS Diode Replacement
Introdução
Ir para o passo 1This guide outlines steps needed to repair an Ubiquiti Unifi AP AC Lite (model UAP-AC-LITE) access point which does not power on, and is identified by the PoE injector having a power fault (blinking white on the PoE injector).
In some cases, affected units' center LEDs may flash dimly when the reset button is held pressed in with the POE power in place. This may only be visible if the board is out of it's chassis.
The UAP-AC-LITE contains an over-voltage protection circuit driven by a unidirectional TVS diode. While this diode is not a fuse, it's expected failure mode is to short, and divert power away from the rest of the board. This short is also detected by the PoE injector, which causes it to not deliver power.
In this guide will show how to:
- Disassemble the UAP-AC-LITE
- Test if the over voltage protection TVS diode has failed
- Remove and replace the broken diode
O que você precisa
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Ferramentas
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Ferramenta utilizada neste passo:Jimmy$7.95
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The front cover is secured by five tabs.
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Use the Jimmy to create a gap near a clip and insert a plastic prying tool. Apply moderate pressure to force the clips open.
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Ferramenta utilizada neste passo:Digital Multimeter$19.99
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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.
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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.
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Ferramenta utilizada neste passo:Tweezers$4.99
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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.
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Ferramenta utilizada neste passo:Digital Multimeter$19.99
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To install the new diode:
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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.
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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.
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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.
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To reassemble your device, reattach front cover.
To reassemble your device, reattach front cover.
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22Comentários do guia
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.
Mine broke in exactly the use case warned against here: https://community.ubnt.com/t5/UniFi-Wire.... 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.
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.
https://i.imgur.com/WvljJ4T.jpg
It gets warm around the silver elko / capacity next to the transformator. But that’s all what I was able to figure out.
would be D28 from what I can see above C556
