BaseBox2 + modem fails

Here is a problem.
I have 2 BaseBox2 devices (both of them worked fine about 2 years).

Now, I’m testing it with my “Ericsson F3507g Mobile Broadband Minicard Composite Device”.

Installed modem, modem works fine.

When i tested my first BaseBox2, some time later, i have noticed, that level of WiFi is very low. And I can’t make it better, even if i update RouterOS, or make default configuration.

I’m testing my BaseBox2 on table, distance is around 2 meters, and on that distance i recieve very bad signal at full power (no_country) and can’t find any wifi, if set russia|regulatory-domain.

After that I took second BaseBox2 with working WiFi, and tested it again with modem. Devices worked fine for about 1 week. After that, I have noticed, that level of WiFi is very low again.

Result is - I can not see WiFi of BaseBox2 if i use /interface wireless set frequency-mode=regulatory-domain (russia, max 20), but when i witch it to manual-txpower, than i see WiFi, but signal is very poor.

I used standard power source (from box) and RBPOE, RBGPOE. I used both devices with standard antennas mounted on it.

Update to “6.40.5” - no result.

Now, when i power on both BB2:
*one round part is very hot, cant touch it (see picture)
*radiatior on other side is very hot too (after 5-10 min of work)

I powered on BaseBox2 only with connected wifi antennas.

When i remove modem, wifi not coming back.

My questions:

  1. What could go wrong? Why both devices fails with the same result?
  2. Does powering on for a short period of time is very dangerous for WiFi controllers?
    wi-fi-router-mikrotik-rb912uag-2hpnd_2.jpg