i have ADSL modems connected to the RB750 ports. Everytime the RB750 reboot, the modems MUST BE turned off first, if not, RB750 won't boot, instead having all ports(1/2/3/4/5) light turned on and it keeps that way until i reboot it. also, every few hours and sometimes, days, the RB750 get rebooted itself, but got stuck because the modems are always on. is there something wrong?

Do you use latest RouterOS and BIOS? I mean 4.10

it runs on RouterOS v4.9

i have another RB750 run on RouterOS v4.9 and has no problem like this. I tried to upgrade to RouterOS 4.10, but it seems the old bug still occur, when i upgraded the RB750 from RouterOS v4.5(default) into RouterOS v4.9. The usual way doesn't work(which is copy - paste the .npk file into Files tab). Doesn't work as, it makes the RB750 into a zombie, it will hang until i do a netinstall to upgrade it. so i decided, to stay on RouterOS v4.9, since the other RB750 doesn't suffer the same problem.

did u change to another PSU?

is it necessary to upgrade the bootloader? because i've found out now that the latest firmware is the main cause of these problems. i downgraded to RouterOS v4.3 and downgrade the v2.26 firmware into v2.22, and the problems are gone now. i currently use v2.22 firmware and RouterOS v4.10 and still OK.

do not use original power suply ... it's small ... try somethink with 12v1a

For 750 12V;0,5A PSU is good enough. For 750G need higher power PSU

For 750 12V;0,5A PSU is good enough. For 750G need higher power PSU

i have not tried 1A adaptor, but the other RB750 i have, all using same adaptors, 0,5A

i say that because i experince that problem many times ...
some rb750 work fine as home router with 0.5Amps ... but some don't ... you can test it like this:
log in with winbox ... go to files ... upload a file ... if the board reboot or winbox stop receive data from rb750 ... or rb750 freeze, you will know the 0.5amps is not good ... i never test if original psu is 6W power or less ... i only replace the psu with 12W power and rb750 start work fine... that all.
you will need more power if the rb750 is use it for high traffic on all port ... you need 15V1A psu minimum

i say that because i experince that problem many times ...
some rb750 work fine as home router with 0.5Amps ... but some don't ... you can test it like this:
log in with winbox ... go to files ... upload a file ... if the board reboot or winbox stop receive data from rb750 ... or rb750 freeze, you will know the 0.5amps is not good ... i never test if original psu is 6W power or less ... i only replace the psu with 12W power and rb750 start work fine... that all.
you will need more power if the rb750 is use it for high traffic on all port ... you need 15V1A psu minimum

that is what happened too, the board reboot and hang, if i upload file. but downgrade firmware and routerOS seems fixing the problem too.

look like the new software need more amps to eat

I note this some times too. It's software bug. Check with different BIOS version.

i say that because i experince that problem many times ...
some rb750 work fine as home router with 0.5Amps ... but some don't ... you can test it like this:
log in with winbox ... go to files ... upload a file ... if the board reboot or winbox stop receive data from rb750 ... or rb750 freeze, you will know the 0.5amps is not good ... i never test if original psu is 6W power or less ... i only replace the psu with 12W power and rb750 start work fine... that all.
you will need more power if the rb750 is use it for high traffic on all port ... you need 15V1A psu minimum

winet, I'm having issues with eth1 on RB750 - three units same problem. As a test stop using eth1 (use another port instead) and see what happens. I would not recommend using older versions of ROS as some reported dropped eth frames on earlier 4.x versions. 3.30 was giving me some issues with VLANs.

Hi, i mean, that I had the same problem, if you have only non-gigabit model ("RB 750"). There was an bug with autonegotiation on each port. When the device was rebooted it was trying to switch itself to Gb mode, but was not able to do it due to hardware reasons. It causes the hang of board and need to switch off and on the power supply.
Mainly i was shocked, when I found in Winbox the aviability to change the mode of ethernet ports to Gigabit mode.
I prefer the 750G model (with faster processor), but i found this problem only on these one non-gogabit device and have no problems with oher five gigabit capable devices.

So, try to change the mode of ethernet ports to 100 Mb half or full duplex, and inactivate the autonegotiation checkbox below. (Unhapilly you must doi it manually with all 5 ports


Good luck !