Just received 2xRB750UP
Upgraded to 5.12, 2.38
Was trying to get one of them working with 3g-Modem.

Got it working with 3g modem, but every 5-10 minutes the light on 3g-stick went red, ether leds on 750UP went down, and only thing that halped was poer reset.
Decided to reflsh firmware again, but it was frozen with all leds on...

So, what I have now is:
* all leds on when powering the device
* holding reset when booting turns eher leds off, but ACT led is still on, and windows says "LAN not connected", so netintsall is useless...

Can I do anything about it?

is it working without 3G modem or you have that unplugged already?

Also, you can attempt to use reset hole on the board to reset configuration.

It's completely bricked up now.
Looks like something went wrong when reflashing firmware. Maybe 3G modem was plugged in, I don't remember now...

So, when it powers on, all lights are ON
Holding reset maked ehernet lights go down, but still no ethernet connection is established (can't use netinstall)...

So, do I get it right: if RB does not even initialise LAN connection, there's nothing I can do with it?

take it out of the box and power up with reset hole shorted to reset configuration, check if it comes up. after reset PoE-out should be turned off (if you had it turned on) then attempt to hold the reset button while powering up the board

edit:

updated with some links
http://routerboard.com/pdf/362/rb750UP-qg.pdf
http://wiki.mikrotik.com/wiki/Manual:Netinstall

I didn't turn POE on.

If I hold reset during power on, all lights turn off, except PWR and ACT. THey both are on. No lan connection...

UPD: Ok, took the case off, shorting reset hole gives nothing - all leds re ON.

http://www.youtube.com/watch?v=cbP6P198bgE

Made a video - in case it's hard to understand what I mean

unfortunately contact your reseller to arrange RMA

That's very sad... But thank you for fast reply.

And, one more thing)
Do I understand it correct - if I buy more expensive model with serial port, I will always have an ability to flash it with NetInstall via serial, in other words, my RB750 could be "unbricked" if it had a serial port?

And, one more thing)
Do I understand it correct - if I buy more expensive model with serial port, I will always have an ability to flash it with NetInstall via serial, in other words, my RB750 could be "unbricked" if it had a serial port?

no! netinstall can be used on any device. serial port only gives ability to see exact problem (error message). netinstall works over ethernet, not serial.

http://rado3105.blogspot.com/2011/12/in ... nsole.html

how to install using netinstall...

here is better link:
http://wiki.mikrotik.com/wiki/Netinstall

here is better link:
http://wiki.mikrotik.com/wiki/Netinstall

Ok. But where can I download netinstall? I go to http://wiki.mikrotik.com/wiki/Netinstall and than it gives me a link to http://www.mikrotik.com/download.html and there I only have a link to http://wiki.mikrotik.com/wiki/Netinstall...

http://www.mikrotik.com/download.html
Next select device from dropdown list.
Netinstall and other files will appear.

HTH,

I had the same problem with 750UP and 3G modem. Does anyone find any solution or justification to this strange behavior? My 750UP put all leds on and lost any eth connection, but I'm able to do netinstall with success. However, when rebooting after netinstall, router returns in previous state (all leds lit and no eth).