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How can I tell if my LNB is going bad?

Discussion in 'C-BAND Satellite Discussion' started by Desertnight, Aug 11, 2009.

  1. Desertnight

    Desertnight Thread Starter Member

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    I have had my Chapparel C-band lnb for quite a number of years. (Don't hold its age against it). The lnb has worked fine for all these years, but now a possibility exists that it is going bad.

    What are the symptoms?

    What can I do to check the lnb and tell whether or not it is going bad or has failed?

    Let's assume for the moment that my receivers are working properly. No failing parts. (I have a DSR920 and a DSR922). I also have a SV360 Elite slaved to one of the DSRs.

    The symptoms of picture quality when the SV360 was hooked up to the DSR920 would be:

    The DSR920 is off while the SV360 is on. -- Picture cuts out -- No signal.
    The DSR920 is turned on momentarily, signal comes back on the SV360. The DSR920 is turned back off. Picture good for a variable amount of time. Then the picture cuts out -- no signal.

    Now, I change all the connections from the DSR920 to the DSR922. No loss of signal. One day later, all of a sudden, the SV360 picture cuts out. I turn on the DSR922 and the picture on the screen (we're talking g4-16--Preacher) is trying to come in, but won't. (I am using G4-16 as the polarity monitor for vertical. G4-17 as the horizontal polarity). The screen keeps flashing the picture, but cuts out).

    If the lnb is failing or has failed, what would be the recommended replacement lnb for c/ku for my 10 foot mesh dish. (I am wanting to change to c/ku anyway for more channels, especially sports).

    Thanks.
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  2. Lak7

    Lak7 SatelliteGuys Family Pub Member / Supporter

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    I wonder if the SV360 outputs enough power for the LNBs or the Servo is not working correctly.
    How is the SV360 connected, High Freq Splitters?
  3. Desertnight

    Desertnight Thread Starter Member

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    I haven't gotten that far yet about checking the voltage cause I just don't know exactly where to check and how to do it. I do have a volt meter with the prongs.

    Also, the lnb was connected directly into the DSR922. Then tried the direct connection to the DSR920 and now have the lnb connected directly to my analog Uniden receiver. Symptoms of bad picture when each of those units were turned on and the SV360 off.

    Thanks.
  4. Lak7

    Lak7 SatelliteGuys Family Pub Member / Supporter

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    I'd check that the Servo is working first.

    Voltage Meter probes are usually too thick to fit into the F Connector, you may have to use a small piece of coax cable.
    The SV360 only outputs 13 or 18 volts (depending on the TPs polarity), and your LNB probably likes 18-22 Volts.
  5. Desertnight

    Desertnight Thread Starter Member

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    Thanks Lak7. I will try the wire.

    Any suggestions for a c/ku linear lnb?
  6. Lak7

    Lak7 SatelliteGuys Family Pub Member / Supporter

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    I use the DMX741 and please with performance.
    I have not used the CK1, other report that it performs good, maybe even better.
  7. truckracer

    truckracer SatelliteGuys Family

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    The dms bsc 421 is a great c band only lnbf and its cheap to buy
  8. Desertnight

    Desertnight Thread Starter Member

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    Thanks for the lnb suggestion, Lak7. :up I check into those lnbs. Truckracer, if I stay with c-band, I'll check on your suggestion.:)

    Here's what the final result is of the bad lnb question:

    I had checked all the connections from the receivers all the way to the lnb. All were good and tight and clean looking. I then took a digital volt meter and checked the volts out at the pole on the cable coming from the receiver going to the lnb. I held the positive probe lead against the copper wire and grounded the negative probe to the pole. Receivers did not have to be "on".

    The DSR920 read a little over 19v.
    The DSR922 read a little over 19v.
    The Uniden analog read a little over 17v.

    Okay...so no problem there with the voltage. So, what was the real problem???
    Something simple??, ...yeah right. Still the lnb???:confused:

    I read somewhere else, this forum or another, where someone was having similar problems and were stumped. The installer finally figured out that the cable going to the lnb was the problem and could have a short in the copper wire inside of it. The cable had been bent.

    My cable to the lnb was bent about 2 inches from the connection at the lnb (short, short loop). So, I cut the cable past the bend and put on a new connector. I left a wide loop in the cable and reconnected the cable to the lnb.

    Voila...everything works again, almost perfectly. No lost signals, etc. Reception very good. So, I guess the lnb is not at fault (at this time). The sun and heat out here beat down on the dish and feedhorn, lnb, without mercy during the summer months. So, I'm sure that contributed to the cable problem.

    Let's hope the problem stays away for awhile until I get a c/ku lnb. :D

    Now, because I changed receivers, I have to "adjust all satellites" on the DSR922 (locations got really messed up) or go back to using the DSR920.:eek:

    Amazing what a person can learn after having a BUD over 20 years.

    :D:D:D:D:D
  9. Desertnight

    Desertnight Thread Starter Member

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    Well, I spoke too soon. The lnb worked fine for a few hours then, kaput! for good.:rant:

    I took the lnb off and opened it up. Found one of the resistors(?), or whatever it's called, FRIED!!!. A little bit of it flaked off on my finger. Now, no tv except local antenna.:eek:

    So, now I am checking into the DMX741 and CK1. Seems the reviews on the DMX741 are favorable. More checking on prices to do also.:)

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