can any one tell me that how to achieve RB2011 Redundant Power Supply with Internal PSU and external PSU. as per a old post of normis in this forum, all new RB can be powered via dc barrel connector power input and POE input simultaneously. i recently install a 19.2 volt laptop adeptor inside my 2011. now i want to know, can i power my 2011uias-RM with that psu and as well as external factory supplied psu also??

here is the mod pic

I think, it depend of schematic of your laptop's PSU.
Better to make power switch, wich will manually (automatic) disconnect 19v wire of "laptop" PSU from motherboard, while connected external "factory" PSU.

but in a old post normis wrote that we can use backside barrel connector and poe input at same time. routerboard use that input which have higher voltage. then why cant we use internal power port and external barrel connector simultaneously. i just want the explanation.

why cant we use internal power port and external barrel connector simultaneously. i just want the explanation.

it depends of schematic of your internal and external PSUs. If you apply external power source to output of internal PSU (or internal power source to output of external PSU), it can damage one of these, even if it not powered on with 220v
You need smart circuit to switch between 2 PSU, or mechanical switch to manually select (manually switching) internal or external PSU

It looks like PSU for 110v or 220v. It can be with manual switch or automatically detects input voltage

Manual switching


Automatic switching

futsker, actually I understand what you want to tell me but as per the old post of normis all modern rb have this automatic switching functionality in built on external dc barrel connector and poe input. now I want to know is the same thing we can apply on internal power port and external barrel connector??

p.s. I already moded internal power with a laptop psu, now I want to apply battery power at dc barrel connector. that's it.

all modern rb have this automatic switching functionality in built on external dc barrel connector and poe input. now I want to know is the same thing we can apply on internal power port and external barrel connector??

i think circuit of PoE input and circuit of power supply at motherboard are not the same. If PoE input has automatic switching between PoEI and external or internal PSU, that doesn't mean automatic switching between external and internal PSU

Related topic: http://forum.mikrotik.com/viewtopic.php?f=2&t=101159

Look at the picture:

You can check voltages at internal power connector when connected external PSU and vice versa - check voltage at external power connector when when connected internal PSU and make conclusion.

It is possible to use two power sources, though it is not supported by manufacturer, of course. Connect both power sources trough diodes like 1N4002 - 1N4007. Anodes to power sources, cathodes connected together and to external power input of RB.

Disclaimer: I am not responsible if You damage something as result of this!