Best way to power an LNB?

[hicks107]

Hi,

Earlier this year I posted about how my S9 stopped giving power on Horizontal TPs. Now I want to resurrect it and want to try providing power to my LNB and motor with a Diseqc or something. Will that work? Can I get a powered diseqc and have it supply the power to the lnb? Will it know when to change between 18/14v? Does anyone know of a product that will be light on my wallet?

Much appreciated,
Mike

 

[FaT Air]

Have you replaced the LNB fuse (Polyfuse)? If so, should be good.
OR; http://www.satelliteguys.us/showthread.php?t=277334

 

[hicks107]

Wow, thanks! I hadnt seen your post before and it came out just after I gave up on that box. I will give that a try. I wonder if my local radio shack will have em in stock. Before I buy one do you feel it would fix my symptoms described last Feb?? Vertical TPs are fine for hours. Horizontal TPs last about 60 seconds and quickly fade away until I get 0 volts.

thanks again,
mike

 

[FaT Air]

Thats the polyfuse. You can just put jumper across it to confirm.
There's members here who may have spares. Digikey is one source. Ratshak, dunno.

 

[hicks107]

That was it. I put my meter on both sides. One read 19v and the other side quickly dropped to zero after about 2 minutes. Im ordering 5 of those. Shipping is pretty cheap. thanks a bunch.

 

[johann12]

Thats the polyfuse. You can just put jumper across it to confirm.
There's members here who may have spares. Digikey is one source. Ratshak, dunno.

I may be wrong on this......
If it is the poly fuse then you would not have either vertical or horizional 14/18 volts output.

 

[johann12]

That was it. I put my meter on both sides. One read 19v and the other side quickly dropped to zero after about 2 minutes. Im ordering 5 of those. Shipping is pretty cheap. thanks a bunch.

Was it the LNB voltage regulator ?

 

[FaT Air]

If it is the poly fuse then you would not have either vertical or horizional 14/18 volts output.

All depends on how badly it(Polyfuse) fails. Mine would drop from around 19V to about 12V and loose horizontal TP's as the LNBF would switch to V. Vertical TP's kept working.
The resistance only goes high enough to reduce the lnb voltage. Doesn't take a over-current situation for it to happen. Calculated mine around 500 ohms.
Operating normally the polyfuse resistance is only a few tenths of an ohm.
With an over-current, the resistance goes extremely higher (~10,000 ohms) and the LNB voltage drops enough to kill even vertical TP's.. wikipedia

 

[johann12]

All depends on how badly it(Polyfuse) fails. Mine would drop from around 19V to about 12V and loose horizontal TP's as the LNBF would switch to V. Vertical TP's kept working.
The resistance only goes high enough to reduce the lnb voltage. Doesn't take a over-current situation for it to happen. Calculated mine around 500 ohms.
Operating normally the polyfuse resistance is only a few tenths of an ohm.
With an over-current, the resistance goes extremely higher (~10,000 ohms) and the LNB voltage drops enough to kill even vertical TP's.. wikipedia

Fat Air,
Thank you for taking the time and explaining this.
I like the wikipedia link.
So someone could use a 500 mA fuse to replace the poly fuse.
As far as I remember the S9 has a 500 mA limit to power the LNB's/LNBF's.

 

[johann12]

I got a question.
If I remember right, the S9 can handle 500 mA output to power LNB's/LNBF's.
Lets say you want to power a motor like the SG 9120 that has a starting movement consumption of 350 mA. Does this mean that you only can power 3 more LNB/LNBF which have about 50 mA each? 350 mA + 50 mA X 3 = 500 mA.
Does this mean that this poly fuse may go bad again, if you go over 500 mA ?
What does someone do if they want to power let's say 15 LNB's/LNBF's from 1 receiver?

 

[KE4EST]

Your not powering all LNBs at once.

 

[johann12]

Your not powering all LNBs at once.

Let me guess.....
That's why we have diseq switches etc. etc. to just turn the LNB/LNBF on that is needed at the time.

 

[KE4EST]

Bingo

 

[johann12]

Bingo

Thank you ke4est

 

[Anole]

That was a good question.
I didn't deal with it in the Switces Simplified FAQ.
... but then, that's not exactly something a novice would worry about, either.

In multi-LNB / multi-receiver (advanced) systems, I would use 2-output LNBFs and Powered multiswitches.
That way none of the LNBFs would display warm-up drift.
And the receiver power supply would never be taxed.