I have a RB740 here that was working just fine and then it started rebooting itself. There were no power issues where it was located so I thought it was a little unusual. Swapped it out with another and when I plug it in, the power light comes on, all the port lights come on, and the act light starts blinking rapidly. The port lights stay on and it stays in this condition no matter how long I leave it.

Pressing and/or holding the reset button does nothing.

Any ideas? Can I reflash this via JTAG? Is there a way to access the serial console? Any onboard "backup firmware" test points I can short to get this thing into a usable state?

It was running 3.29.

Thanks

what kind of PSU are u using with? can u check in the PCB if is there any failure capacitor

i'm using the Power supply that came in the box with it. Also, I don't see anything wrong with the capacitors on the board. Granted, I haven't czeched them electrically (yet).

do u have a multimeter to test the voltaje output? or try with another PSU, just to discard, and after what happened to u?

I've tried it with 3 different power supplies from other RB750s we have here. \

try to install the routeros with netinstall put the cable in ether1. read the manual at wiki

If you reset the router, insure the computer you are trying to access the router from is connected to ports2-5 and use 192.168.88.1 to access the router. Port 1 is set to dhcp client., so you almost have to login to find the ip of that port. Don't mean to get really simple, but sometimes I forget stuff like that.

hi I have same problem
the ethernt ports of my rb750 are up but I can't connet to OS .
also I can't reset it with two place that there are on the board.
is it a hardware problem and software hardware?

Is it ACT led goes off after power on RB?

yes , it gees off after power on

see This
http://forum.mikrotik.com/viewtopic.php?f=3&t=45610