Hello!
I bought around 600 pc. HAP AC Lte Tower (RB952Ui-5ac2nD-TC) from different distributors in Russia.
250 pc. of them heve problems with USB Power. We check around 50 pc. with different 4G modems and power supplues.

When i discovered this problem i wrote in support ([SUP-4729])
Antons B. from support ask me to make test with USB HUB with external power.
I checked. With External power work normaly. But i can't use this way for 250 pc.

I want my money back for 250pc. with sn xxxxxxxxxxx/936 and /937
Russian distributor: 3logic

[SUP-4729]
When we try to upload files, modem swich off and then swich on... loose connection. You can see it on attached video.

https://yadi.sk/i/zSlnMHl44xomcA
https://yadi.sk/i/2mjzWoL4wI8mjQ


Work normaly on HAP AC Lite with another sn:
like
sn: A2280A037271/901/RU

First of all, I can feel your frustration.

One has to understand the traditional USB powering limitations. hAP ac lite features USB 2.0 and standard max power output is 500mA. It is common practice that most USB ports offer higher current (docs of hAP ac lite specifies maximum USB power output of 1000mA), but if USB device requires more than 500mA, that's out of specs and one should not blame USB host for not supplying arbitrary amount of power. So first you should check (official specs and online forums) the maximum power draw of your LTE device. Perhaps even measure actual power draw through USB port. And if the actual power draw is considerably less than 1000mA and hAP ac lite still drops voltage low enough for LTE modem to restart, then you have case to claim refund (or exchange with devices which can actually output 1A over USB port).

So
I took a power measurement and video:

https://yadi.sk/i/Wm8ziLB6inmN8g

Max Load (when upload) 0,44 A,
Mikrotik make USB power reset.

Metering device could have delay, but:
at 0.448A it is visible only 4.04V.
Possibly that 4.04V can occur because of USB power cut-off.
But also possible this case: USB voltage dropped due to high load, and as result modem resets itself due to low voltage...
Without oscilloscope it's not possible to understand what's the source of problems.

Cabling also adds Voltage drop

Cabling also adds Voltage drop

Have you seen the video posted above ? No cabling there at all.

Sorry to necro post on this but it accurately describes my problem. I have a sn xxxxxx/933 version of this router and the USB voltage is 4.95V at 0mA sagging to 4.75V at 150mA.

Was there any resolution to this? I'm out of warranty and open to reworking the pcb.