GL-AR150 Hardware Failure

npkamen · 2017-11-21T07:28:57.000Z

Hi there,

I just had to replace my AR150 and am trying to understand the failure so I can try to determine the cause of it.

Here is my setup:

Solar powered comms tower (https://i.imgur.com/3xjtpY8.jpg)
12V from solar to battery converted to 5V via DC-DC converter
AR150 powered via DC-DC converter and has USB LTE modem connected for internet access

I recently went up there as I had lost comms to it and found the following:

Dead 12V-5V DC-DC Converter
Dead AR150

I popped the cover off the AR150 and found the following chip completely blown (U6).

Replaced the DC-DC converter and the AR150 and all is happy again. I realise that the AR150 isn’t open source design but it would be nice to know what the U6 chip is so I can rule some things out.

Can anyone shed some light on this for me?

spacix · 2017-11-22T05:14:59.000Z

Looks like you blew the power input, what happened to the 12V to 5V buck converter? My guess would be it shorted out and fed 12V into the router’s power input.

npkamen · 2017-11-22T05:38:24.000Z

That is my guess as well. I intend to dissect it to find out. It is one of those sealed units but hasn’t shown signs of failing (other than not working) so it’ll be interesting to see what it looks like inside.

spacix · 2017-11-22T07:45:57.000Z

Well most little LDO’s for 3V or 5V regulation normally have a max input of about 7V to 9V. I’m not sure what part is on the AR150, the marking on mine is “AZ 91” and I found a LDO by Richtek ( https://www.rom.by/files/Richtek_Marking_Code.PDF ) but the only 8-pin is a WQFN 1.6x1.6-8 which is not the correct size for the part for U6; but the surrounding passives indicates it is a regulator of some type.

npkamen · 2017-11-22T08:03:17.000Z

Thanks for that. That validates the theory of the DC-DC converter causing the fault. Whether that was due to a surge on the 12V side or not I’m not sure. I do have an Ubiquiti Nanostation connected directly to that 12V side and it survived without issue so we can probably put this one down to the buck converter failing. It’ll be interesting to see what it looks like when I pop the cover off it.

spacix · 2017-11-22T09:35:42.000Z

You could add some over voltage protection circuity to the output of the buck converter to make it a more proper power supply, if it continues to be a issue.

npkamen · 2017-11-23T16:31:19.000Z

Yeah thanks I’ll see how it goes now. I’ve installed a much larger and (relatively) more expensive buck converter this time so hopefully this one doesn’t give as much grief.

Unfortunately I must have thrown the old one out as I can’t find it any more so not going to be able to look any further.

Chalk this one down to experience I suppose.

glitch · 2017-11-23T17:22:18.000Z

I have a theory - how about a lightning strike?

npkamen · 2017-11-23T17:59:53.000Z

Yes I did think of that. Few problems though:

None of the 12V equipment had an issue (charge controller as well as Ubiquiti Nanostation)
The USB LTE modem seems to work ok (it powers up at least and I can access the web interface in the modem). It did have some trouble connecting to the network though so theoretically it could be blown too but I am yet to test it. I had to replace it on the day just to get things up and running. There are a number of explanations for this one though which I need to investigate first.
The pole is earthed with an earth stake so that should provide the best path to ground for a lightning strike.
If it was a proper lightning strike I would have expected to see much more damage. The tower (6m mast) is high on a hill however there are some fairly close trees (both alive and dead from previous lightning strikes many years ago) which I would have thought would also provide a bit of cover for my little tower.

Definitely worth some thought though.