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Guest Message by DevFuse

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How to tell if LNB is faulty?


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6 replies to this topic

#1 OFFLINE   abc123

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Posted 02 February 2014 - 09:28 AM

Hello Forum,

 

I have a Dish 500+. It was working fine for a few months. Yesterday I thought I heard some snow pack slide on to it from the roof top and immediately lost signal. 

 

I figured the alignment went bad, but after spending 2 hours I have still been unsuccessful to get any kind of signal on any of the satellites (110, 118 and 119). Normally it does not take this long to catch signal, about 10 minutes of trial and error gets me the signal. But I have ZERO signal this time. 

 

Question: Could the falling snow/ice have damaged the LNB and how can I find out via diagnostics if that is the case?

 

Thank you in advance for your help!

 

Here is the check switch result: 

 

Under Details: 

============

Switch Status: Connected to a DPP 500+ with 4 inputs

DPP 500+-2 Good Connecton, No Signal 

External LNB: N.C. No Connection 

 

 

Install Summary:

=============

 

Input:             1           2          3           4

Satellite:     Conn    Conn     Conn       X

Polarity:          X          X           X          X

Device:         DB+      DB+       DB+     N.C.

Status:           Problem detected, check connections

 

SuperDish - CHECKED           Alternate - UNCHECKED

 

 

 



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#2 OFFLINE   P Smith

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Posted 02 February 2014 - 11:23 AM

Question: Could the falling snow/ice have damaged the LNB and how can I find out via diagnostics if that is the case?

 

Nope.

Using DMM  (direct connection to LNBF) it should show ~20 kOhm resistance.

Measure voltage during switch check: must be +13VDC to +18 VDC switching

 

Umm, uncheck Superdish in menu

 

D500+/D1000+ is tricky to aim w/out a device like satfinder or more advanced.  Get 119W first, then fine tune to 118.75W for max level, then check 110/129W wings.


Edited by P Smith, 02 February 2014 - 11:28 AM.

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#3 OFFLINE   harsh

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Posted 02 February 2014 - 12:21 PM

First, eyeball the mast to see that it looks plumb and that the locking nuts at the foot haven't galled the paint by sliding.

If you don't see visible damage to the LNB, arm or reflector, check where the arm bolts to the dish mounting bracket to make sure nothing is wrinkled.

If something is bent, it is much easier to replace it than it is to fix it. The 118.7W positioning is very critical and a simple hammering out may not be sufficient.
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Too often we enjoy the comfort of opinion without the discomfort of thought. -- JFK


#4 OFFLINE   abc123

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Posted 03 February 2014 - 12:12 PM

Thank you very much for the replies. I did manage to catch signal for all three sats 110, 118 and 119. However it is only displaying channels for 110 and 119, can't get channels for 118. I have read that 118 is the toughest of them all, will continue to fine tune it to see if I can get 118 channels also. 

 

In the check switch summary for Sat 118 it says Polarity as "Even".

 

For the other two sats 110 and 119 it says "All" for Polarity. 

 

What does the "Even" mean? 


Edited by abc123, 03 February 2014 - 12:20 PM.


#5 OFFLINE   P Smith

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Posted 03 February 2014 - 12:51 PM

even mean only even tpn numbers, ie signals coming with H polarity , and no V signals from the LNBF, so check skew setting of your reflector too


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#6 OFFLINE   abc123

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Posted 03 February 2014 - 01:41 PM

even mean only even tpn numbers, ie signals coming with H polarity , and no V signals from the LNBF, so check skew setting of your reflector too

 

 Thank you for the pointer. Skew is pretty accurately set as per the guide for my zip code. If any, the AZ and EL are the ones I feel iffy about. The bolt setting for the EL is a tricky one. My dish doesn't have a line for the skew setting, it just has a bolt and I am trying to take the outside periphery of the bolt to coincide with the EL setting for my zip. 

 

Used the info from this thread to do that setting: http://www.dbstalk.c...sh-500dish-500/

 

The AZ is tricky also, but I did manage to catch to catch the signal. 

 

Could the AZ or EL also be responsible for the 118 not getting full signal or is it only the Skew setting that is doing it? 


Edited by abc123, 03 February 2014 - 01:43 PM.


#7 OFFLINE   harsh

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Posted 03 February 2014 - 02:14 PM

Bolts aren't the correct reference for setting the elevation.  If you look in the slot, there should be an edge (referred to in the instructions as "Edge") of the sheet metal underneath that in some cases is/was painted red (and on some dishes, is tapered down to a sharp edge).  This edge is what is to be used to set the elevation.

 

Note that if you haven't verified that the mast is plumb, you're wasting your time.  If any of the bracketry appears bent, you're also wasting your time.  If none of the settings appears to have slipped, then something is probably bent.

 

Here's the installation instructions:

 

http://www.sadoun.co...nstructions.pdf

 

I stole the following VERY, VERY USEFUL image from a post by BattleZone:

 

dishassemblyElevation.gif


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Too often we enjoy the comfort of opinion without the discomfort of thought. -- JFK





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