Advice Needed On communal satellite system

[Archive4]

Trying to sort out a problem for a friend today ( who helped me lift a 1.4 dish yesterday into an impossible position, near death experience! ) when I found an unusual problem.

Old tv with stb works ok ( ish ) pixels even on strong txp´s so there is a problem with that which I will take up with the company who put the system in.

The main problem, when you attempt to fit a new TV, stb states no signal. I have managed to work out that new tv ( only two pin connection ) and old tv ( three pin connection ) one works , one does not. Have also worked out that if I earth the two pin stb on the new two pin tv signal comes back up.

Tested incoming cable and approx 7v ac from the screen, thus knocking out the signal from the dish/ multiswitch. Made a manual earth connection to the stb and all ok, but without, nothing.

I would have thought that the multiswitch should be earthed to prevent this, but this is Spain! Cannot access the equipment due to locks, but have told my mate I will prove the problem to the guts who fitted the system if required.

Any thoughts from the revered members of the forum who are used to dealing with such systems?

 

[jeallen01]

You have to be very careful if you try to earth to the TV with the 2-pin lead because that means that it is Double Insulated - so any exposed metal on the set is heavily insulated from the mains circuits, and don't anyone try opening up the case and searching for something that might be "earthed/grounded" because it probably isn't.

However it's probably OK if you make a connection to the shell of the output socket (or the case, if it is metal) of the stb as that is designed to be user accessible, and thus "safe", and make sure the earth/ground goes back to the ground contacts (the spring side contacts) in the wall socket (not to a radiator or such like). Also worth seeing if reversing the plug in the socket makes any difference because one of the two mains conductors is the Neutral which is grounded at the incoming supply point to the premises.

BTW: I had to do something like the above when I had hum loops on the AV equipment, most of which was also Double Insulated - made a connection from the chassis of the AV amp to the mains socket and the humming stopped. That also helps to avoid the cumulative effects of the leakage currents to the chassis from the RFI filters in each of the AV units - the leakage from 1 unit is very low indeed, but connect a lot of them together and it can become "noticeable"!

 

[A nonymous]

Put it to the company that installed the system regarding pixilation. I would also be tempted to try another receiver to see if the earthing issue persists.

Not going into it anymore as i'm on my second bottle of 1l house white and its already taken me a few mins to write this

Its in my house and its my wine so its house wine as far as i'm concerned

 

[Lazarus]

White House wine, shirley?

 

[Archive4]

Thanks Jeallen01, but I am an experienced electro-mechanical engineer, with a specialism in telecoms, so know the do´s and dont´s with relation to electrical issues.
Manic, already tried a stb of the same type, then tried with my solo se, same problem. Used a bit of blue wire ( no yellow and green to hand ) to connect from the socket earth to the outer on the " input " of the stb and signal returned ok. Tests with multimeter advised 7v ac from outer of coax to earth. As I asked, should the multiswitch be earthed, thus passing the earth to the outer of the coax feeds to destination?
Please answer after bottle 3, it will be more colourful !

Lazarus, don´t complicate the issue, it´s any colour he likes

 

[Channel Hopper]

Is any output of the multiswitch going off to a receiver or TV that is not part of the supply phase of the property ?

 

[Terryl]

Thanks Jeallen01, but I am an experienced electro-mechanical engineer, with a specialism in telecoms, so know the do´s and dont´s with relation to electrical issues.
Manic, already tried a stb of the same type, then tried with my solo se, same problem. Used a bit of blue wire ( no yellow and green to hand ) to connect from the socket earth to the outer on the " input " of the stb and signal returned ok. Tests with multimeter advised 7v ac from outer of coax to earth. As I asked, should the multiswitch be earthed, thus passing the earth to the outer of the coax feeds to destination?
Please answer after bottle 3, it will be more colourful !

Lazarus, don´t complicate the issue, it´s any colour he likes

Now where did you find a coax that is 12.75 KM in diameter?

On a more serious note......If you have any AC voltage on the coax shield then there may be a power supply problem back at the switch, (if it's a power switch that is) 7 volts AC is not much but it can mask the Diseqc command signals back to the switch from the receiver(s).

Another possibility is that the switch or coax ground is bad/corroded/not installed, and it's a ground loop problem, all coax entering the house (or other dwelling) needs to be grounded with a coax ground block.

It could be that the person that install it got lazy and snagged the local electrical ground at the wall socket, this could cause all sorts of problems.

I always use a ground rod when possible.

But if you do have a source for coax in that diameter please forward the link and I'll have a few scotches while I await delivery.

 

[Archive4]

Is any output of the multiswitch going off to a receiver or TV that is not part of the supply phase of the property ?

TBH I have no idea, my friend has a feed from the community system. No keys to access the multiswitch ( es ) and nobody around to ask, Saturday in Spain, nothing unusual! From what I could see, dish ( 1.8 pf ) on roof of property 36, in total about 60 properties although not all connected to the system. Chances of all being on the same phase, none, hence the need for earth at root, ie multiswitch, where ever it is.
This could be a long story!

( Sorry Terryl, posting this as you have done yours )

 

[Channel Hopper]

OK, rip it all out and start again, it's the only way to be sure.

 

[PaulR]

Do regs in Spain not state that the multiswitch should be earthed on the outer of the co-axial? There are blocks that can fitted to the outputs (and inputs) to the multiswitch to achieve this in one go.

If there is such a reg then it may be safe to assume that it has been done, to an earthing rod even as Terryl suggests.

But you already know that you need to look at the multiswitch(es) to be sure.

 

[Archive4]

TBH I'm not sure of the regs in Spain as I have never fitted a community system. Have worked on a couple to rectify cable faults but not much else.
Have told Steve to contact the president of the community to get the original installers or maintenance people to investigate first. Would like to be there though so have told him I am happy to meet them to show them the problem.