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jmnet

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Reply with quote  #1 
Today on one of my C-Band dishes I cannot get any vertical signals.  I have an ortho feed so 2 C-Band LNBs.  Seem to have no horizontal polarity problems.  The feedhorn is tight so it is not moving.

So in troubleshooting, I discovered my power injector was only passing 7.8 volts to the LNB not the 18 it should be.  I replaced the power injector and verified I have 18 volts to the LNB, actually it is 17.8, but close enough.

So, could I have fried the LNB because of the under-voltage to the LNB?  Not sure what else could be the problem.

Thanks.

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majortom

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Reply with quote  #2 

It is possible that whatever caused the power injector to fail, also took out the Horiz LNB?
Lightning strike nearby maybe, and the Vertical LNB just got lucky?
For Kicks, maybe...I would try swapping the Horiz & Vert LNBs around to be certain??
Should be able to do that without disturbing the rest of the feedhorn, alignment wise.
You could also compare the current being drawn by each LNB. The dead one would be drawing
significantly different current than the working one. If they were drawing nearly the same current
I'd still be scratching my head. I am assuming they are the same brand & model.




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Perfect 10 7.5' mesh Chapparal C/Ku Co-Rotor feed, Norsat 8115 CBAND, Norsat 4106A Ku Thomson Saginaw Actuator, Vbox positioner,
Home Brew Polarotor683 Servo circuit. Openbox S9, Prof7500, v4l-updatelee linux drivers installed.
ricardo's geo-orbit archive: https://web.archive.org/web/20071202191450/http://www.geo-orbit.org:80/sizepgs/tuningp2.html
jmnet

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Reply with quote  #3 
Quote:
Originally Posted by majortom

It is possible that whatever caused the power injector to fail, also took out the Horiz LNB?
Lightning strike nearby maybe, and the Vertical LNB just got lucky?
For Kicks, maybe...I would try swapping the Horiz & Vert LNBs around to be certain??
Should be able to do that without disturbing the rest of the feedhorn, alignment wise.
You could also compare the current being drawn by each LNB. The dead one would be drawing
significantly different current than the working one. If they were drawing nearly the same current
I'd still be scratching my head. I am assuming they are the same brand & model.





That's my next step to swap the two and see what happens.  Way too many lightning storms around this year.  One going on right now.

How can I tell how much is being drawn?  I just put a meter on the core of the coax to see how much is being sent.

Thanks.





__________________
===========================
Don't blame the computer! It does exactly what it's programmed to do!
--------------------------------------------------
Solar Energy Generated As Of 8/31/16: 78.551 Megawatt hours!!!
Receivers: Pansat 9200HD, Manhattan 1933, AZBox Premium Plus, Linkbox 8000, Prof 7301 x 2 Dishes: (2) 10' C/KU BUDS, 100cm Fortec Star
majortom

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Reply with quote  #4 
Basic electricity.
To measure "Voltage" we place a voltmeter in Parallel with the source or load.
To measure "Current", we place an ammeter in Series with the source or load.

We can measure the DC Current being drawn carefully, by
1.) disconnecting the coax to the LNB
2.) complete the DC Current Path from the coax to the LNB by bridging the Shield of the coax
to the shield of the LNB using an alligator clip test lead.
3.) set your DMM to DC mA, and make sure to plug the Red Test Lead of the meter in to the corresponding DC mA Jack of the meter.
This makes it an "ammeter".
4.) place the DMM in series with the coax center conductor and the center Conductor pin of the LNB.
Can insert a small paper clip or resistor lead about the same diameter as a coax center pin, in to the center pin of the LNB.

Took a snapper of this setup from the basement floor, at the USB Tuner end of a run going out to the Primestar Antenna. Which is basically the same thing, but measuring at the opposite end from what you'd be doing. The original Primestar LNB appears to draw ~ 340 mA while on Horiz.
I used an old capacitor as a lead to plug in to the LNB connection of the DVB USB Tuner involved.
You don't want to permanently spread the Center Pin Socket of the LNB by using something TOO BIG for it.



Attached Images
Click image for larger version - Name: lnb_current_test.JPG, Views: 23, Size: 153.04 KB 

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Perfect 10 7.5' mesh Chapparal C/Ku Co-Rotor feed, Norsat 8115 CBAND, Norsat 4106A Ku Thomson Saginaw Actuator, Vbox positioner,
Home Brew Polarotor683 Servo circuit. Openbox S9, Prof7500, v4l-updatelee linux drivers installed.
ricardo's geo-orbit archive: https://web.archive.org/web/20071202191450/http://www.geo-orbit.org:80/sizepgs/tuningp2.html

jmnet

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Reply with quote  #5 
Quote:
Originally Posted by majortom
Basic electricity.
To measure "Voltage" we place a voltmeter in Parallel with the source or load.
To measure "Current", we place an ammeter in Series with the source or load.

We can measure the DC Current being drawn carefully, by
1.) disconnecting the coax to the LNB
2.) complete the DC Current Path from the coax to the LNB by bridging the Shield of the coax
to the shield of the LNB using an alligator clip test lead.
3.) set your DMM to DC mA, and make sure to plug the Red Test Lead of the meter in to the corresponding DC mA Jack of the meter.
This makes it an "ammeter".
4.) place the DMM in series with the coax center conductor and the center Conductor pin of the LNB.
Can insert a small paper clip or resistor lead about the same diameter as a coax center pin, in to the center pin of the LNB.

Took a snapper of this setup from the basement floor, at the USB Tuner end of a run going out to the Primestar Antenna. Which is basically the same thing, but measuring at the opposite end from what you'd be doing. The original Primestar LNB appears to draw ~ 340 mA while on Horiz.
I used an old capacitor as a lead to plug in to the LNB connection of the DVB USB Tuner involved.




Thanks.  That's something I'd like to try just to know how to do it. 
I opened up my injector and it looks like a capacitor blew up.  I attached a picture.  It didn't bulge, it split at the top.
 cap2.jpg


__________________
===========================
Don't blame the computer! It does exactly what it's programmed to do!
--------------------------------------------------
Solar Energy Generated As Of 8/31/16: 78.551 Megawatt hours!!!
Receivers: Pansat 9200HD, Manhattan 1933, AZBox Premium Plus, Linkbox 8000, Prof 7301 x 2 Dishes: (2) 10' C/KU BUDS, 100cm Fortec Star
majortom

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Reply with quote  #6 
hmm, where exactly? I am not seeing it.
Can you place an arrow or draw a scribble around it?
The yellow looking goop looks like a silicone type of stuff they use to keep it stable from vibrations??


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Perfect 10 7.5' mesh Chapparal C/Ku Co-Rotor feed, Norsat 8115 CBAND, Norsat 4106A Ku Thomson Saginaw Actuator, Vbox positioner,
Home Brew Polarotor683 Servo circuit. Openbox S9, Prof7500, v4l-updatelee linux drivers installed.
ricardo's geo-orbit archive: https://web.archive.org/web/20071202191450/http://www.geo-orbit.org:80/sizepgs/tuningp2.html
majortom

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Reply with quote  #7 
http://www.dummies.com/programming/electronics/how-to-measure-current-on-an-electronic-circuit/

The battery in that diagram you can think of as your power insertor.
The series resistor can be your run of coax. The A in the diagram is your DMM setup to measure DC mA,
and the LED can be your LNB.

That is basically what your looking at.

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Perfect 10 7.5' mesh Chapparal C/Ku Co-Rotor feed, Norsat 8115 CBAND, Norsat 4106A Ku Thomson Saginaw Actuator, Vbox positioner,
Home Brew Polarotor683 Servo circuit. Openbox S9, Prof7500, v4l-updatelee linux drivers installed.
ricardo's geo-orbit archive: https://web.archive.org/web/20071202191450/http://www.geo-orbit.org:80/sizepgs/tuningp2.html
jmnet

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Reply with quote  #8 
Quote:
Originally Posted by majortom
hmm, where exactly? I am not seeing it.
Can you place an arrow or draw a scribble around it?
The yellow looking goop looks like a silicone type of stuff they use to keep it stable from vibrations??



I think you're right.  That was what I thought leaked out, but at real close inspection with my bad eyes, and a blown up picture, it is on top and not leaking.  Anyway, something is broke inside that won't output enough juice.


__________________
===========================
Don't blame the computer! It does exactly what it's programmed to do!
--------------------------------------------------
Solar Energy Generated As Of 8/31/16: 78.551 Megawatt hours!!!
Receivers: Pansat 9200HD, Manhattan 1933, AZBox Premium Plus, Linkbox 8000, Prof 7301 x 2 Dishes: (2) 10' C/KU BUDS, 100cm Fortec Star
majortom

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Reply with quote  #9 
Could be one of or more of them Diodes. Don't know if you can get to both leads of them or not to test the junctions. Could also be the device that is heat sunk to the chassis (probably a 3 terminal Voltage regulator.). If you can read the part number of it with a magnifying glass we can probably find the datasheet for it, which would explain how it works, and usually has a typical circuit diagram.

Of course you would test the diode junctions without any power applied to the unit under test.
But here is an example:
http://en-us.fluke.com/training/training-library/test-tools/digital-multimeters/how-to-test-diodes-using-a-digital-multimeter.html

__________________
Perfect 10 7.5' mesh Chapparal C/Ku Co-Rotor feed, Norsat 8115 CBAND, Norsat 4106A Ku Thomson Saginaw Actuator, Vbox positioner,
Home Brew Polarotor683 Servo circuit. Openbox S9, Prof7500, v4l-updatelee linux drivers installed.
ricardo's geo-orbit archive: https://web.archive.org/web/20071202191450/http://www.geo-orbit.org:80/sizepgs/tuningp2.html
biggt

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Reply with quote  #10 
Well, I'm in the same boat but I lost the horizontal side. I noticed after a really bad storm. I tried two different paths into it and neither one worked. I will tear into it later but all signs point to a bad lnb or a bad multi-switch.
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jmnet

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Reply with quote  #11 
Quote:
Originally Posted by biggt
Well, I'm in the same boat but I lost the horizontal side. I noticed after a really bad storm. I tried two different paths into it and neither one worked. I will tear into it later but all signs point to a bad lnb or a bad multi-switch.


Well, I can deal with a $32 fix to get a new power injector, replacing the LNB is going to hurt cost wise, to replace it like for like.  It's a Norsat 3220, I believe.


__________________
===========================
Don't blame the computer! It does exactly what it's programmed to do!
--------------------------------------------------
Solar Energy Generated As Of 8/31/16: 78.551 Megawatt hours!!!
Receivers: Pansat 9200HD, Manhattan 1933, AZBox Premium Plus, Linkbox 8000, Prof 7301 x 2 Dishes: (2) 10' C/KU BUDS, 100cm Fortec Star
GFM

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Reply with quote  #12 
Fixing these things (power injector) can be fun and educational... and parts are really cheap! [smile]
Use the good injector on the suspect LNB and see if it works... but maybe check the LNB for a short before hooking it up... just in case!

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-36"Ku with SG2100 & PLL321S-2 --... ...--
jmnet

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Reply with quote  #13 
Quote:
Originally Posted by GFM
Fixing these things (power injector) can be fun and educational... and parts are really cheap! [smile]
Use the good injector on the suspect LNB and see if it works... but maybe check the LNB for a short before hooking it up... just in case!


The fun continues.

So I swapped the cables between the 2 LNBs.  My expected result was instead of getting all Horizontal signals no Vertical, I'd get the opposite, all Vertical and no Horizontal.  The result was all Horizontal and no Vertical.  So basically I'm getting Vertical signals on my Horizontal path so my LNB is working fine.  That's a big sigh of relief. That means there is an issue getting the Vertical signal back to the receiver.  And since there are multiple receivers/PC Cards connected to these LNBs, I suspect the multiswitch has gone bad.  If only one receiver failed, then I can point to the receiver, but all, it has to be the common component.  Now I need to dig through my box of old gear and see if I can find one.  My first test will be to bypass the multiswitch and be sure all is well.  Fortunately this is happening in July and not the fall when football season comes around.



__________________
===========================
Don't blame the computer! It does exactly what it's programmed to do!
--------------------------------------------------
Solar Energy Generated As Of 8/31/16: 78.551 Megawatt hours!!!
Receivers: Pansat 9200HD, Manhattan 1933, AZBox Premium Plus, Linkbox 8000, Prof 7301 x 2 Dishes: (2) 10' C/KU BUDS, 100cm Fortec Star
jmnet

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Reply with quote  #14 
Turns out the problem was with an inline amplifier in the cable run.  Taking that out of the equation got my vertical back.  Something fried my power injector and this amplifier.  Cheap fix thankfully.
__________________
===========================
Don't blame the computer! It does exactly what it's programmed to do!
--------------------------------------------------
Solar Energy Generated As Of 8/31/16: 78.551 Megawatt hours!!!
Receivers: Pansat 9200HD, Manhattan 1933, AZBox Premium Plus, Linkbox 8000, Prof 7301 x 2 Dishes: (2) 10' C/KU BUDS, 100cm Fortec Star
Pops

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Reply with quote  #15 
Congrats! [thumb]
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