Lnb feed causing ground loop

[blakmumba]

Hi, having a really strange problem. The lnb coaxial feed into my sat box (which only has 2 pins - no earth - icecrypt s4000) is causing a ground loop and making a really loud hum through my subwoofer (kef 1000.2). If I connect a wire from the lnb coaxial f connector at the back of the sat box and attach that to 1 of the screw on the Kef 1000.2 the hum TOTALLY vanishes but my receiver goes into 'protect mode' and switches itself off until I disconnect the wire!.
Would earthing the icecrypt cure this? And if so, how would I do it.
Many thanks

[echelon]

Hi, having a really strange problem. The lnb coaxial feed into my sat box (which only has 2 pins - no earth - icecrypt s4000) is causing a ground loop and making a really loud hum through my subwoofer (kef 1000.2). If I connect a wire from the lnb coaxial f connector at the back of the sat box and attach that to 1 of the screw on the Kef 1000.2 the hum TOTALLY vanishes but my receiver goes into 'protect mode' and switches itself off until I disconnect the wire!.
Would earthing the icecrypt cure this? And if so, how would I do it.
Many thanks

the icecrypt s4000 has a standard F connector ( 2 actually ) and one lnb feed should go to each F connector in order to use both tuners

the outer braid is always the lnb earth and the inner conductor the main feed , so ensure the outer braid is actually touching the F connector and ensure the inner solid copper core is not touching the F connector

there should be no need to earth or ground the icecrypt (or any other sat box for that matter)

seems to me that your F connector connections have not been done correctly

[vinny0048]

Have you got your digital out from the Icecrypt to your Av receiver by coax or optical? I have had this prob with my Kef 1000.2 sub when I had a TM9100. I simply switched from coax digital out to optical out and the hum disappeared.

Let us know how you get on.

[blakmumba]

Thanks for the replies guys.
@echelon - have just re-done all the f connectors the way you instructed above but to no avail (the hum is still there). Could it be that I'm using a F connector socket to socket coupler?). I'm only using a single lnb feed to my icecrypt (twin tuner) but have chosen single tuner only in the settings (got quad lnb) also not using loop through.

@Vinny0048 - have tried everything mate. Hdmi lead to carry the audio, optical out etc but honestly nothing and it's driving me nuts. Have tried 2 different subs and av receivers AND 3 different sly boxes (currently icecrypt but also ggg hd and dream box 500) that work at mates houses but get the dreaded hum at mine. It's only when I connect a wire with 1 end attached to the f connector at the rear of the icecrypt and the other to an earth point (screw on the kef sub) the hum vanishes. When the receiver is on standby the hum becomes really loud but once out off standby it vanishes?

[mister-t]

i had a simmilar problem but not reciever related
the problem i had concerned a sony turntable and a loud hum,i tried everything to cure the hum,turn turntable off no hum from speakers turn it on hum appeared,in the end sony sent engineer out
baffled him for a while then he said i am getting feed back from turntable to speakers,he told me to move turntable away from speakers,which i did while he was there and it worked,now i am not saying thats your problem but anything is worth a try,also seeing you only get this hum with subwoofer on while receiver is on maybe just causing you some sort of feed back,like pointing microphone at a speaker makes hi pitch sound

mister-t

[echelon]

Thanks for the replies guys.
@echelon - have just re-done all the f connectors the way you instructed above but to no avail (the hum is still there). Could it be that I'm using a F connector socket to socket coupler?). I'm only using a single lnb feed to my icecrypt (twin tuner) but have chosen single tuner only in the settings (got quad lnb) also not using loop through.



if you are using both tuners in single feed mode you should actually be using a coax cable of say a foot long , with f connector at each end

connect the outside lnb to lnb 1 input , then connect the loop cable from lnb 1 output to lnb 2 input

the outer metal housing of an F connector is the earth up to the lnb , with the centre core carrying 13 volts or 18 volts as required

there should be no need to connect an earth wire from the icecrypt to the sound system

ideally use a shotgun cable from the quad lnb and feed both tuners separately

do not use any form of splitter or combiner for this , just a standard loopthrough cable with f connectors and ensure the braid isnt touching the centre core but is touching the f connector metal housing

I am not sure what you mean by socket to socket coupler ?

[blakmumba]

I am not sure what you mean by socket to socket coupler ?

It's when your coaxial cable isn't long enough you add this coupler to extend the wire (basically attaches 2 separate coaxial cables together). If you follow the link below it shows you the picture of the coupler. My problem is ONLY happening when the AV receiver is switched OFF and not when on. Its honestly really bad and have to continuously power off the sub from the mains or remove the input wire from the sub which is annoying. Echelon why do you think that when I touch the lnb f connector with a wire and then earth the other end the humming/loud buzz disappears? Unfortunately I cannot keep the wire there as my receiver goes into 'protect mode' and powers down until I remove the wire.

THANKS everyone for replying, means a lot :)
Coupler picture link

http://www.google.co.uk/search?hl=en&client=safari&gl=uk&biw=320&bih=356&tbm=isch&btnG=&q=lnb%20coaxial%20coupler#i=21

[echelon]

It's when your coaxial cable isn't long enough you add this coupler to extend the wire (basically attaches 2 separate coaxial cables together). If you follow the link below it shows you the picture of the coupler. My problem is ONLY happening when the AV receiver is switched OFF and not when in. Its honestly really bad and have to continuously power off the sub from the mains which is annoying. Echelon why do you think that when I touch the lnb f connector with a wire and then earth the other end the humming/loud buzz disappears? Unfortunately I cannot keep the wire there as my receiver goes into 'protect mode' and powers down until I remove the wire.

THANKS everyone for replying, means a lot :)

Coupler picture link

~_http://www.google.co.uk/search?hl=en&client=safari&gl=uk&biw=320&bih=356&tbm=isch&btnG=&q=lnb%20coaxial%20coupler#i=21

so you mean a back to back f connector coupler , commonly known as a "barrel connector" - that wont have any bearing on this as long as the f connectors are correctly put on

seems to me from your description that when you connect the icecrypt earth ( like say the outer f connector ) to the sound system they are at the same potential , whereas when you dont it seems that the icecrypt is at a different potential than the sound system , thereby you hear mains hum caused due to a potential difference

I do not have a sound system and so have never tried what you are asking , but I do not think you have an lnb problem as clearly you are using and watching the icecrypt

therefore I will move this to the icecrypt section

[blakmumba]

Ok thanks for the helping as its much appreciated :)

[kenedwards]

Here's a possible cause of your problem.
Does your Icecrypt have a Euro-type 2-pin mains plug? (possibly with a UK adapter plug).
If so, then if you reverse the plug (just turn it through 180°) in the adapter if used, and see if that helps.
With non-earthed equipment like this, this type of problem can occur. I used to have this sometimes when living in Germany.