We have an issue on RouterBoard RB1100AHx2, for the first boot it was working fine but while i were trying to intall another RouterOS packages it suddenly stopped working/initializing and it failed to boot.
Always it gives a crackling noise sound and it seems like it cannot boot, and we tried to access the RouterBoard unit itself by all possible ways likes (Ethernet, Boot port,and Console..) but it’s not work and accessible at all.
We already do the “RESET” the device by the boot backup reset button but still the same issue.
Anybody can help and provide us a good solutions on this issue? 
That sound while booting is normal behaviour for RB1100AHx2.
You need to reinstall the router with Netinstall to get it back working:
http://wiki.mikrotik.com/wiki/Netinstall
The crackling sound is repeated, it seems like it is rebooting every second, and sure we tried to reinstall the OS by Netinstall but it’s not bootable at all.
We tried to do everything to boot but it still not.
Please advice.
What is printed in Serial Console during boot process?
Can you access BIOS configuration menu from Serial Console?
Make sure Netinstall PC is connected to ether13 port of RB1100AHx2.
There nothing printed on the console and we can’t access BIOS configuration menu.
And about Netinstall PC : It is connected to port 13
Hold reset button while turning on the router and check if there is something printed in Console (default baud rate: 115200).
If Console shows backup booter loaded, try to access BIOS configuration menu.
Actually we did as you said exactly , but we couldnt access the BIOS configuration , its seems rebooting every second and I think it isnt normal sound , it’s weird .
We tried it more than one time by the way .
Please advice.
This RB1100AHx2 seems to be unrecoverable, it could be a hardware fault.
You should contact the company where this RouterBoard was purchased regarding warranty options.
as fot the reboot loop you have to open the routerboard case / hold the reset button and plug the power cable in the same time
at the putty console you will se the bios turning on type any key in keyboard so you saty in bios menu ,/ then follow the net install procedure that is shown in mikrotik manual
in my case i just read & reread & reread the netistall procedure , i did connect mu rb 1100 ah x2 with serial com port null cable/ to a normal pc opened putty with baund 115200 , let mu router in loop restart for a while / then i opened the router case with my screwdriver & i presed the reset button meanwhile plugin the power cable in & holdig the buuton for at least 30 seconds the my router entered in bios mode
this procedure did help me , so thank you guys for puting a light in this kind of problem
I had the same issue, it gave a crackling noise sound and didn’t boot. Don’t know what caused that, but i often had some sudden power failures and power issues - i guess this caused the boot failure.
I had to open it up and reset the device and use Netinstall and followed the procedure in the following URL
http://wiki.mikrotik.com/wiki/Manual:Netinstall
Its working fine now (at the moment - cant say about the future).
Regards