LNB Issue?

azzeretti

I have an odd problem I have not come across before. I have quad LNB on an old MK3 dish. This feeds two boxes in the house. Over the last few weeks I've noticed that if just one of the boxes is powered up I get no signal. However, as soon as the second box is switched on the signal is fine to both boxes.

In the past I would just replace the LNB, to test, but for various reasons, I'm not in a position to do that without being certain of the problem first!

Anyone ever seen anything similar?

Thurston?

Yeah, it's a situation that's come up here before. (Can't think of a search term to get a link.)

IIRC, OPs weren't up for even basic troubleshooting e.g. checking cables, looking for water ingress, so threads went nowhere. No 'expert' help on hand either ...

pegasuspub

check the earth connections on the f connector plugs at the lnb,
this problem is normally caused by a bad connection on the earth screening of the cable at the plug by the lnb,
disconnect the receiver from the power and cut back a few inches of the cable and re make the connections if possible.

Gerry Wicklow

Is it the same box that is dead when the other is off? Bit of a long shot but it could be a connection problem. The ground outer mesh of the coax is common. If the dead box had a broken ground connection it might be getting it's ground from the other box once it is plugged in. (If that makes sense)

SNAP.pegasuspub beat me to it

Thurston?

I doubt any box has been plugged out, or any other mechanical break in the circuit.

Problem is a bit more subtle I'd think, but could be wrong ...

steveon

Is it a sky box or a fta box that you have? Check the settings on the box and make sure lnb power is switched on both boxes, this sounds like your problem to me as if its switched to off on the second box it would need the first box to be powered up etc.

Thurston?

steveon wrote: »

Check the settings on the box and make sure lnb power is switched on both boxes, this sounds like your problem to me as if its switched to off on the second box it would need the first box to be powered up etc.

If that is the 'problem', powering the other box up shouldn't make any difference, the LNB outputs are supposed to be independent of each other in that respect.

azzeretti

steveon wrote: »

Is it a sky box or a fta box that you have?

No, they are two Vu+ boxes.

It gets stranger. If the two boxes are off and one is switched on you tend to get "No signal", if you switch them both on the signal increases. If you then switch one box off you can continue watching the other box fine - It is strange.
I've ruled out the boxes though, I've a couple of other dishes up (after my motor and 1.1 blew off to Holyhead in the stormy winter ) and there is no issues with these dishes connecting to the same box(es).

Looks like I'll have to get up there and check LNB connections, bah....

EDIT: It's not the same box each time, both boxes exhibit the problem, depending on which one is switched on first.

Thurston?

This specific problem has only ever been mentioned here with Sky LNBs, so some of them must have an inherent weakness that causes them to behave like this.

Maybe water getting in, causing circuits to interact, that shouldn't interact?