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Repair a Ubiquiti Bullet Titanium BM2-TI after over voltage short circuit

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Unread 03.01.17, 04:33 PM
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Post Repair a Ubiquiti Bullet Titanium BM2-TI after over voltage short circuit

Hello Everyone,

First, I would like to say thank you UBNT for wonderful engineering.. It is nice to see robust products.

I just wanted to share with the community an experience with a BM2-TI Bullet.
https://www.ubnt.com/airmax/bulletm/

Officially, any voltage applied to the BM2-TI over 24.5V DC can damage the unit. This unit was hit with a standard 48V POE power supply by mistake.

When the correct 24V POE was connected back to the unit the LEDs on the unit blinked on and off at the same time n sync with the blue power light on the POE supply. This LED error reading indicates a short in the LAN cable or the unit. I know the cables used are in good working order.

Please understand this will VOID all manufacture warranty and is not recommended if your product is still under warranty.

This unit was going on 2 years of operation and was rock solid. I would have a new one from the mail in 2 days, but no internet was a drag !!!! So let's open the device..

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After some poking around with the voltage / ohm meter I found a shorted surface mounted diode D5" on the PCB next to the LAN port.

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A part that looked like this shorted once the maximum reverse voltage of 24.5VDC was reached to protect the unit from being damaged.

I did not have the correct surface mount diode at the time. So, I found a diode substitute off a power PCB on a 4 head VCR.

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Understand, I no longer have reverse voltage protection with this device using the 1N4001 diode as it will reverse short at 50V vs. 24.5V and burn up the device, but the device is back up and running. If I stumble across the correct part I might replace it. It will be my backup device anyway once the new unit arrives.

Until then, I made sure to make a series of labels "24VPOE". I placed them on the Cat6 network cable at the switch leading from the device, on the POE brick, and on the external case of the Ubiquiti Bullet Titanium BM2-TI.

There is no want to repeat the mistake !!!!


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