PowerBOX RB750P-PB @ 290ft, will not power 2nd Device

Hardware MikroTik hardware general
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Hey Folks!

So, have been working with a PowerBOX and its shipped 24v 2.5a power supply. We have 5 of these units, and all have the same result. The system was configured and benched but with only 30ft of cable from injector to PB. But failed once we put it up on the tower. The PB powers up and is accessible from the ground, but fails to power up 1 or all four of the SXT SA5’s. So now I am benching in the office to find a solution.

The setup on the tower is> 24v 2.5a power supply > mikrotik supplied gigabit poe injector > 290 ft of ubnt tough cable > PowerBOX RB750P-PB > 4 10ft ubnt tough cables > 4 SXT SA5’s

The setup on the bench is very close to the same> 24v 2.5a power supply > mikrotik supplied gigabit poe injector > 290 ft of ubnt tough cable > PowerBOX RB750P-PB > 6ft molded cat5> 1 BaseBox 2 w/WLAN disabled

Both of these setups have the same result. The PB is running and accessible, but the attached devices do not power at all. There are no lights illuminated on the attached device(s). And there is an audible clicking that can be heard on the PB.

In both instances the PB see’s 21.7v’s present. So the available wattage to the PB is technically just above 54 Watts, this should be sufficient to boot the one BaseBox2.

I am in the process of acquiring a 30v power supply, but given the theoretical math, I am not sure that will be a solution.

I also have installed a 24v ‘Reducer’ in line attached to the PB (http://www.enableit.com/enableit-products/PoE%20Reducer/324.php) , in conjunction with a 48v 1amp PS. This results with 23.7v’s seen at the PB with 1Amp available. This produces the same result as above.

With the PowerBOX’s advertised intended use, this seems like an unlikely result. Obviously a guranteed solution would be to shorten the cable length, but to what extent? And why, what am I missing?

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Thanks to wiltshra , http://forum.mikrotik.com/t/if-your-rb750up-poe-out-wont-work-when-powered-by-poe-in-read-below/86735/1 I found this solution.

http://wiki.mikrotik.com/wiki/Manual:PoE-Out#Global_settings

On the bench this works. I will post my on-site results when I get them.

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UPDATE:: On the bench this DID work when adding a BaseBox2 and a BaseBox5, but when adding a third device (METAL-9hpn), it would brown out and reboot all of the devices, which is actually odd given the POE priorities should have just that 3rd device fail.

Again, the above is with 290ft of cat5 between injector and PB.

So, I believe it is safe to say that the PowerBOX will not power 4 SXTs reliably. Which is really too bad, I thought these were going to help out on our upgrade path.

If this took in 56v POE, and stepped down to 24v for the attached devices, it sure would have made this much more useful.

I’m starting to think that an investment opportunity is becoming more and more attractive. To build hardware for RouterOS that actually meets the demands of real WISPs, and in a timely manner. Love routerOS, but the HW is getting too cheap.