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Old 07-03-2019, 04:47 AM   #1
Join Date: Sep 2018
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Default Ubiquiti Nano Loco M5 5ghz, does not turn on, internal buzz

Hi all

Receive a warm greeting

I have a LocoM5 unit, water came through the holes of the LED diodes.

The unit does not turn on but a buzz is heard.
checking internally the board did not find any component in short circuit.

Check the integrated circuit: VR3 AOZ1212. The output voltage on pin 1 is 1.69vdc when you touch the pin4 with the tester, the power led and the buzzing sound frequency change were turned on.

Interestingly, if I put my finger on that pin, the unit turns on the led, the voltage goes up to 4.9 vdc. and the buzz stops being heard.

The LAN LED lights up. If I connect the unit to a switch it gives me an IP address and I can see the AirOS configuration website. (I can not enter since I do not have a username or password).
The client told me that this unit is the receiver, and since I have not worked with these devices before, I do not know if the signal LEDs should turn on or not in this state. or if they only do it when they receive a signal, also this unit is 5Ghz.

The signal LEDs remain off. In that zone, rust is observed. (Yellow Zone)

I measured the voltage at C91 and C92 and it's 4.52vdc. (area protected by metal mesh) (Red Zone)

What can be the problem, any suggestions.
How to test the chips that are inside the maya, red zone

I measured continuity between both pins of the antenna and it shows resistance close to zero (1 ohm approximately antenna vs gnd), however, I have a Crazy M2 unit and it marks the same, can I assume that this is normal?

Check the other voltages.
RAM 1,8vdc
CPU, 3.3vdc
Chip Atheros. 2.5vdc
VIN: 24vdc.

Please if any of you can give me a guide of what things I can review and try, I thank you in advance.

Thank you.
Attached Images
File Type: jpg M5 (6).JPG (92.4 KB, 5 views)
File Type: jpg M5 (1).JPG (199.9 KB, 7 views)
File Type: jpg M5 (2).JPG (199.6 KB, 8 views)
File Type: jpg M5 (3).JPG (168.3 KB, 5 views)
File Type: jpg M5 (4).JPG (173.6 KB, 5 views)
File Type: jpg M5 (5).JPG (115.8 KB, 5 views)
File Type: jpg M5 (7).JPG (162.1 KB, 6 views)
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Old 07-19-2019, 03:07 PM   #2
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Default Re: Ubiquiti Nano Loco M5 5ghz, does not turn on, internal buzz

I would probably take my meter and check how many ohms are reading on either side of some of the power rail capacitors. You might have a short that is pulling something to ground. For instance, you mention that touching your finger across some of the pin tends to start things back up. That could be because some corrosion is keeping the "reset" pin pulled to ground (or pulled high depending on the chip.) It could also be that something has gone higher resistance, such as a resitor on a voltage sense circuit/divider.

But yes, I would check on either side of some of the capacitors on those power rails and just see if anything shows up with a lower resistance..

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