Forum > Decoders > Installation > blown LNB after plugging SD decoder into HD multiswitch with TV-Link still on
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Old 2014-07-21 , 14:15
garybenade garybenade is offline
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Question blown LNB after plugging SD decoder into HD multiswitch with TV-Link still on

I have a HD PVR connected to a LNB via a 2 to 6 multiswitch. The PVR was using RX 1 -> 4

A SD decoder was plugged into this multiswitch on RX5

The decoder had TV link set to on (it was being used for extra view previously)

The LNB is quite old, and does not have surge/voltage protection

The HD PVR started malfunctioning a few hours later, some channels were blank, and the HD channels have no sound

The second channel now shows 63% signal, when it used to have 100%

My theory is that because the TV-Link was still active the 2nd decoder was feeding extra voltage into the LNB via the multiswitch, causing damage to one of the ports.

The installer is saying it is just coincidence that the LNB blew on the same day that the second decoder was added. I am skeptical

Could this setup have damaged the LNB?

Any thoughts would be appreciated
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Old 2014-07-21 , 14:28
gwalker gwalker is offline
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Quote:
Originally Posted by garybenade View Post
I have a HD PVR connected to a LNB via a 2 to 6 multiswitch. The PVR was using RX 1 -> 4

A SD decoder was plugged into this multiswitch on RX5

The decoder had TV link set to on (it was being used for extra view previously)

The LNB is quite old, and does not have surge/voltage protection

The HD PVR started malfunctioning a few hours later, some channels were blank, and the HD channels have no sound

The second channel now shows 63% signal, when it used to have 100%

My theory is that because the TV-Link was still active the 2nd decoder was feeding extra voltage into the LNB via the multiswitch, causing damage to one of the ports.

The installer is saying it is just coincidence that the LNB blew on the same day that the second decoder was added. I am skeptical

Could this setup have damaged the LNB?

Any thoughts would be appreciated
Hi and Welcome

TV Link power is on the RF OUT port and doesn't connect in anyway to the LNB Ports unless incorrectly connected.

65% signal strength is very low and would indicate the dish is out of alignment. 100% quality on such low strength doesn't make sense.

The voltage of TV Link is 5V compared to the LNB going upto 18V. Very unlikely the SD Decoders TV Link had anything to with damaging the LNB.

The LNB is external and exposed the elements.
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Old 2014-07-21 , 14:35
garybenade garybenade is offline
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Thanks for the quick reply

Nothing was touched on the dish itself, and all channels had 100% before the decoder was added. What else could cause 65% signal on the one channel?

Is it at all possible that the 2nd SD decoder being connected to RX5 caused the problem? Could it have send 18V to the 13V LNB port perhaps?

Thanks again, your advice is really appreciated
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  #4  
Old 2014-07-21 , 15:13
gwalker gwalker is offline
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Quote:
Originally Posted by garybenade View Post
Thanks for the quick reply

Nothing was touched on the dish itself, and all channels had 100% before the decoder was added. What else could cause 65% signal on the one channel?

Is it at all possible that the 2nd SD decoder being connected to RX5 caused the problem? Could it have send 18V to the 13V LNB port perhaps?

Thanks again, your advice is really appreciated
The multiswitch would need to be faulty to blow a decoder.

Always best to make sure there are no shorts on the cables. And when connecting equipment that all power is off while connecting and disconnecting.

I assume this is an academic exercise to find the root cause of the problem?

I would let Brian and Geoff have a stab at this.
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Old 2014-07-21 , 15:21
Optimist Optimist is offline
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With all the adjustments that were going on it is possible that a short caused an issue, as Graeme says one should always disconnect everything from the power before making adjustments.
But normally nothing you do on the decoder side will effect the standard voltages that are sent to the LNB by the MultiSwitch, nor can a damaging or for that matter any increase in voltage occur.
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Old 2014-07-21 , 15:26
garybenade garybenade is offline
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My initial theory was that the LNB had blown due to over-voltage caused by the TV-link, but since that cable is no longer connected and the voltage is just 5V this is definitely not the cause

All channels are working, the HD channels don't have surround sound. I can only record 1 channel, in the past I could record 2 simultaneously

The installer is coming around tomorrow to replace the LNB.

At this point it would be valuable to know if the symptons point to a blown LNB, or just a misaligned dish
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Old 2014-07-21 , 15:33
Optimist Optimist is offline
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An LNB fault is far more likely than a misalignment here.

I suggest unplugging the decoder for a couple of hours, that has helped others at times before (but no certainty it can help you).

As for the rest, best to wait for the installer tomorrow and see what develops from there.
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Old 2014-07-21 , 17:06
gwalker gwalker is offline
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Quote:
Originally Posted by garybenade View Post
My initial theory was that the LNB had blown due to over-voltage caused by the TV-link, but since that cable is no longer connected and the voltage is just 5V this is definitely not the cause

All channels are working, the HD channels don't have surround sound. I can only record 1 channel, in the past I could record 2 simultaneously

The installer is coming around tomorrow to replace the LNB.

At this point it would be valuable to know if the symptons point to a blown LNB, or just a misaligned dish
Make sure the installer ensures the Dish has clear line of sight (no tress in the way). Also that he uses a DVB-S2 compliant FSB and tells you the reading in dB should over 11 dB, I think MC accept 9dB's. Also check the cabling is still fine and not perished.
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  #9  
Old 2014-07-21 , 21:44
Geoff D Geoff D is online now
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AND check the MULTISWITCH.
It sounds like a MS problem caused by a short on one of the cables.
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  #10  
Old 2014-07-22 , 09:16
garybenade garybenade is offline
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Thanks Geoff!

The cable connected to RX5 was shorting.
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