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grounding problems with CA/411U casing...

Posted: Mon Nov 28, 2011 5:29 am
by saintofinternet
hi,

I have installed a RB711UA-2HnD board in a CA/411U casing. (Picture attached)
IMAG0241.jpg
Now when i insert the Power Supply (i.e. 24v DC) in the Wall plug and the other end into the routerboard I can feel current passing through the entire casing even before switching it on. The wall plug has been tested for earthing and has no issues.

I just fail to understand why this happens.

Re: grounding problems with CA/411U casing...

Posted: Mon Nov 28, 2011 9:48 am
by saintofinternet
help....

Re: grounding problems with CA/411U casing...

Posted: Mon Nov 28, 2011 10:00 am
by normis
before switching it on? so power jack is not plugged in? :) how is that possible.

make sure nothing is touching the board, i see your antenna pigtails are touching, maybe they are shorting something.

Re: grounding problems with CA/411U casing...

Posted: Mon Nov 28, 2011 10:06 am
by saintofinternet
even if i keep the board outside the enclosure with the pigtails connected the same things happen.

i am really frustrated... i have to deliver this to the client and now this absurd thing is happening....

Re: grounding problems with CA/411U casing...

Posted: Mon Nov 28, 2011 10:08 am
by saintofinternet
before switching it on? so power jack is not plugged in? :) how is that possible.

make sure nothing is touching the board, i see your antenna pigtails are touching, maybe they are shorting something.

power jack plugged in at both the ends... but not switched on. i can feel slight vibrations on the body when trying to touch the enclosure.

Re: grounding problems with CA/411U casing...

Posted: Mon Nov 28, 2011 10:13 am
by normis
what do you mean by "not switched on", there is no on/off switch! when you plug in, it's switched on.

anyway, try to figure out any potential touching points, where does something touch the case.

Re: grounding problems with CA/411U casing...

Posted: Mon Nov 28, 2011 10:19 am
by saintofinternet
hi normis,

not switched on meaning the adapter not switched on when plugged into the wall socket (220v AC)

also the points of contact are
1. the 4 mounting screws in the enclosure.
2. the pigtails with N connector (bulkhead) coming out of the enclosure from behind.

as i said when the board is unmounted and kept aside with the pigtails still connected the same thing happens. i can feel the current in the enclosure.

anything connected to the board in any metal form is making this happen. how can i overcome this issue?

-sid

Re: grounding problems with CA/411U casing...

Posted: Tue Nov 29, 2011 3:53 pm
by jonashi
it sounds like a problem with your power supply. Did you try another power supply i mean galvanic isolated (not switching PSU, but transformer based?). If you have PSU with on/off switch, turning off your power supply it usually does disconnect "hot", in this case 12-28V or mains 220V wire too, however ground remains still connected, so if there is some problem with parasitic current flowing from outlet to output of your power supply this should be it (it could be for example faulty capacitor in the circuit or something in insulation between HOT - Mains 220V and PSU output.
I can't imagine single reason why this could be routerboard related, when routerboard is not connected to any antennas yet.
In case it does appear when it is connected to some aerial system, that is another case, there is a posibility to induct parasitic current on the long wires and can be solved by another countermearures.

Re: grounding problems with CA/411U casing...

Posted: Tue Nov 29, 2011 5:58 pm
by saintofinternet
what kind of another countermeasures?? :) and hey jonashi thanks for the detailed reply.

Re: grounding problems with CA/411U casing...

Posted: Thu Dec 01, 2011 9:53 am
by jonashi
this is a bit more complicated. Is your wifi antenna all alone on the pole? Or shares the pole with another antennas (TV radio etc.)? How is your pole grounded? Maybe simpliest way to analyze this is to take a multimeter, and measure AC voltage between your RB case ground/Nfemale and pigtail ground /Nmale, when they are not connected yet.. in case there is some voltage, try to measure current too. There could be a ground loop... for example if you can, try to disconnect all other devices using some antenna on the pole from outlet /AC220V. If problem cousing TV.. you can insert capacitor between ground of TV connector and ground on antenna cable to fix... However as your pole configuration is unknown, Im giving only wild guess.

Re: grounding problems with CA/411U casing...

Posted: Thu Dec 01, 2011 7:24 pm
by saintofinternet
no pole... it is an indoor unit. you can refer to the photo at the start of this thread.

Re: grounding problems with CA/411U casing...

Posted: Thu Dec 01, 2011 9:10 pm
by jonashi
so that means "other countermeasures" is meaningless. So have you tested different power supply? Have you measured voltage between ground in the AC outlet and your RB case? Or you can test run your configuration on UPS without AC to UPS connected - only on battery and problem should disappear. I'm confident that your problem is your powerilnes/AC 220V or power supply related.