ExpressVU: Help Diagnose Missing Even Transponders

[JVMiller]

I'm hoping someone can help me diagnose this problem -- I don't know enough about how the system works, so I'm looking for some pointers...

A few weeks ago, we were unable to get some channels on our ExpressVU system (multiple receivers experienced the same problem). It turned out we were getting no signal from ALL even transponders on 91. We have a dual LNB dish with two outputs per LNB. After swapping the cabling between the two LNBs (I had to do this both on the inside and outside, why?), I've managed change the problem. Now we have no signal from ALL even transponders on 82.

At the advice of technical support, I tried to re-aim my dish. All that ended up doing was landing me lower signal strength than I started with (I really had a perfect aim before!)

I've tried replacing the switch (SW44), the power inserter, and the power inserter power supply one at a time with a neighbors to see if it was the switch, but no dice. I cant remember if I ran a check switch after replacing the switch -- does that matter?

I'm pretty sure I'm dealing with either a broken LNB (how often does this happen?) or bad cabling (couldn't find any visual clues as to the problem after inspecting the cables, but I haven't looked right where the cabling attaches to the LNB). What can I do to narrow it down further?

Also, with the two LNBs, does one LNB have two outputs for the SAME dish, or does each LNB have one output for 82 and one for 91? I can't see anything on the LNB that indicates which dish it's supposed to receive -- or is this a property of it's location on the dish mounting bracket? I have a spare LNB, but I don't know if I can just replace it, or if it will only function on one side of the dish, or if the multiple outputs have any special significance (or are they interchangable as far as their connection to the SW44 is concerned?)

I don't know how accurate the signal strength display on the point dish application is, but I think I've seen it blip signal for the even transponders. I wasn't sure if this was legitimate, or an artifact of signal on a different transponder, as I have a hard time reproducing this, and it seems to happen around the same time I switch from a working transponder to a non-working one.

Would really appreciate it if anyone could help me out, or give me some tips on what to try next? Sorry for all the questions.

 

[Smith P.]

Just call and schedule tech visit. You mentioned enough info to troubleshoot and if it didn't help you, then it's time to call.

 

[Slartibartfarst]

Judging by what you say you have exchanged and still you have the problems i think you are correct in thinking it must be a cable or connector problem.

I would say to put all new connectors on the cables. Then if that does not work try using a spare piece of RG6 cable to replace each section of cable 1 by 1.

I would guess it must be the short jumpers between the LNBF's and the inputs of the SW44.

The LNBF's are identical to each other, it just depends which location they are fastened to in the "Y" adapter on the dish as to which bird they are picking up. As you moved the problem from 91 to 82, you have proved that it is not your LNBF's.

 

[JVMiller]

Thanks very much for the information -- I'm probably going to give it one more shot before I buckle and call someone out. As you said Slartibartfarst, I'm considering spooling out some RG6 straight from the

Is there a sane way to test a length of RG6 with a multimeter? What if the two ends are a long distance apart? How about if I wire straight from the LNBF to the receiver (via a male-male adapter in my utility room), and visit the point dish screen to measure reception from all transponders on the satellite associated with the LNBF I'm connected to, one cable at a time? Will this be an accurate cable test? Do I have to run check switch or can I just ?

While performing more tests today, I noticed that signal strength on the even transponders would occasionally jump to 100 for a length of time here (even up to 30 seconds or more), and after changing transponders it would go back to zero. Is this a tell-tale sign of cabling issues?

 

[JVMiller]

Oh, one more question. Does anyone have a link that describes how the signaling is done over the coax? I'm interested to know how exactly it works, and what can cause just the even/odd transponders to lose signal.

 

[SJ44]

Is there a sane way to test a length of RG6 with a multimeter?

Put a 75 ohms terminator at one end of the cable and check with the tester at the other end.

- around 75 ohms: ok
- near 0 ohm: cable short
- very hight reading: cable open

 

[peano]

I bet its a connector.

 

[Slartibartfarst]

I agree with Peano......

 

[jcm123]

I have found that the even transponders are much weaker on 91 (possibly on a different satellite) and if the dish is misspointed, has paint on it's surface or the LNB is slightly "off" you will loose the even transponders. Another cause is a screwed up "check switch". Make sure that you run that as a first check - easiest to do.
Hope this helps.