Hoping someone out there with more satellite system than I has some ideas for troubleshooting the following problem.

System: DirecTV with two receivers (Sony/Phillps) each attached to a separate LNB. I am also running DirecPC off the same dish. I should mention that I have some pretty long cable runs to all three systems. The Sony is over 100' but has an inline booster doohickey in the cable (not separately powered). All three systems (sony, phillips, internet) have pretty good signal high 70's to high 80's.

Problem: Usually the Phillips receiver is not in use and is turned off, but when someone watches tv on that system for a while eventually the singal strength on the other reciever (Sony) will drop to zero on most but not all of the channels. Turning the phillips receiver on/off doesn't fix the problem, but I have discovered that tuning the Sony receiver to a channel that has dropped to 0 signal and then turning the Phillips receiver to the exact same channel makes the signal return on the Sony receiver. I haven't exactly diagnosed what activity on the phillips receiver makes the sony one go bad, and I can't make it happen on command. However, it does SEEM like it happens mostly when the phillips receiver is used for a longer stretch of time. Could be changing channels a lot, or maybe just allowing it to heat up, but who knows.

At this point I think something is defective in the system, but I can't imagine what. Looking for educated guesses on whether a receiver (and if so which one), the LNB, or the cabling is the likely culprit and maybe troubleshooting steps to isolate which one.

You have a wiring problem or a bad LNB. This problem would occur if you had only one feed coming down from the satellite LNB, split somewhere to feed the two receivers. Or if the LNB were bad, with two outputs are acting as one (I have seen this once before).

Are there three thingies up there on the dish? One would be the DirecTV receive LNB, one the DirecPC receive LNB, one the DirecPC microwave transmitter, which is why the instructions tell you not to stand in front of the dish when everything is powered up.

The DirecTV LNB should have two RG-6 coming off of it, one going to the Philips, one going to the Sony. The DirecPC has two RG-6, going to the transmit and receive connections of the chassis near your computer. If three wires come down, then one of those comes from the DirecTV LNB and is split somewhere.

First, though, you need to know that when you "turn off" a satellite receiver, it does not go off. Its outputs go off, but otherwise it acts just as though it were on. That is why you can leave it off for a month but it has an up-to-date guide when you turn it on. That is why it stays warm, too. That is why this problem does not go away when you turn it off. If you disconnect it from the power, though, it will be what you and I consider OFF and the problem with the other receiver will go away. This will work both ways with your setup unless there is also a problem with the amplifier.

The satellite receivers send a DC voltage up to the LNB to tell it which polarity of signal to look for, which corresponds to even or odd transponders, but does not correspond to any recognizable pattern of channels.

If both satellite receivers on a signal split from one LNB are sending the same voltage up to the LNB, then both will receive a channel. If one sends the low voltage and the other sends the high voltage, the LNB will act as though only the high voltage is being sent, and that receiver will work. If they both send up the same voltage, be it high or low, they will both work.

That is why sometimes they both work, and if they are on the same channel, they definitely are sending up the same voltage. If you find a couple of channels where one receiver works and the other one doesn't, try reversing which receiver is on which channel: the other one should then be the one that works.

And please let us know!

If you really have two outputs from that LNB, and it is not the case that someone has split a single output, then your LNB is bad.

Incidentally, I have used an amplifier when I thought there was a signal problem and the measured signal number went down. The number some undefined measure of quality, not signal level, and if the amp made the signal too hot, its quality could be lower. Try your setup without the amp to see if the number increases. I have run over 200 feet of RG-6 without an amplifier with signals in the 80s. I used amps once, but those were runs over 300 feet, which DirecTV said could not work. The amps were in the middle of the run.

This message was edited by Ernie Bornn-Gilman on 10/09/05 15:04 ET.

There is a small LNB with two wires going out (one to each receiver), and a third wire coming out of a really large LNB looking thing (which I assume is the DirecPC LNB) since it has the transmitter thingy mounted on it too with a wire going into it. Sorry, I was wrong in my original post about having a separate LNB for each receiver, It is a single LNB with two outputs. So it sounds pretty much like I have a bad LNB based on your post. As I understand it, an LNB is a pretty cheap part and as long as I don't move the dish, I could probably easily replace it myself. I will come back and post whether it worked or not.

Thanks a million for the advice. I tried explaining this to the DirecTV support line but they basically troubleshoot with me until I get both tvs working (using the technique above), then they act like there isn't a problem and don't want to help me anymore.

Tricky is definitely the word for this one. It might look like I just had this one knocked, but when it first occurred to me, it involved six satellite receivers in two buildings a hundred feet apart, and people used the receivers differently, so it looked like about twelve problems. I think it was about eight hours of head-banging over two weeks before I figured it out.

DirecTV doesn't expect that. Because of my experience with that house, I might be able to bring it down to a paragraph that would stump them, but they just can't get it all over the phone.

Be sure the replacement LNB looks identical and is not labeled as an "LNB C."

Hope I'm not to late to help but here goes. If I were to go to a house with the problem you describe the first thing I would do is find out if the PC side of the dish is an independant feed (because I have never had to install that style dish before). Based on what you have written it sounds like it is. Second, swap the physical locations of the two receivers. If the problem follows the sony than you can rule out the wiring and the LNB. If the problem stays, leave the receivers in their swapped locations and goto the dish, undo the LNB and swap the two feeds. If the problem switched to the other receiver again the LNB should be replaced. If the problem is still in the same place, (on the phillips receiver which is still in the sony's original location) than the LNB is still good and the line and hardware between the dish and receiver is the culprit. I think it is very likely that the inline amp is a problem. I have seen many of these fail regularly. Try taking this out and replacing with a regular barrel connector. I have many installs with upto 200'-250' of line with no need for an amp so I question wether you really need it or not. Also, is it located at the receiver or the LNB? Location placement can make a very big difference on the strength of the signal that the receiver is receiving and several of the transponders are very sensitive to that level.

Hope this was insiteful.

By the way, I would not be surprised to find out that you have a bad sony receiver. I have seen them go bad often and some have done some really bizarre things. (Especially with the 55 and 65 series).

8's:
The problem as I describe it would follow the Sony and would also still be present if you swapped wires at the LNB, but your description gives two results for these two things. I don't think he tried the same sort of thing with the Philips to see if it acted JUST like the Sony (but he didn't happen to do the same button pushes).

When I solved that problem at that house that I mentioned, one of the big bafflers was that one receiver was in the nursery, one in the living room, one in the office (different building), and each one was used for different channels. The problems appeared to be different from receiver to receiver. The answer only showed up when I tried exactly the same thing on each receiver and found that they all behaved identically.

And YUP ! The inline amp could be the source of the problem, especially if it somehow kept 18 volts from getting up to the LNB. You are right; he MUST test his setup by putting an F81 in place of the amp. That alone might fix it.

jfuex,
8's suggestion about where the amp is placed is really valid, too. If it is at the LNB, the amp will be receiving a signal too hot for it to amplify. That is like turning the volume up to 13 when you only have 10. If the amp really is needed, it should be placed far enough down the line (150 feet minimum) that the signal has decreased below the maximum that the amp can cleanly amplify. Again, if you remove the amp and ANY of the signal measurements increase, or even stay the same, then the amp is doing no good and could be making your signal problems worse. Fortunately, though, not actually hurting any gear.

Hey Ernie,
I'm assuming that you are referring to your first response about having a feed from the LNB being split and I agree that my normal troubleshooting would not have found the source of that problem but would have succeded in causing much cursing and fist pounding. I didn't take that situation into consideration because jfuex confirmed that he did have a seperate feed from the LNB to each receiver.

I also have run into this problem once in years past and thanks to your explination, I now understand the technical reasons for the absolute screwed up symptoms I got that day. I did find the splitter and new it was evil for no better reason than it was rated for 950mhz and dss is in the 2 - 2.2 ghz range. All is clear now. Thanx

Hey jfuex,
I'm still wondering if your all fixed up.

Isn't the range of symptoms, even now, just AMAZING? The one I was troubleshooting had the dish on the garage and two leads going over 100' to the house. They wanted to add a receiver in the garage, so I used a couple of splitters and a 2 in, 2 out multiswitch to provide a signal for the garage unit. In the dust and the sweat of the fibreglassy attic, I obviously (now) connected the splitter outputs incorrectly.

The garage unit was hardly ever used, but the polarity it was on determined whether half the house didn't work. Some days everything was just fine. Actually, on those days the garage unit might not work, but nobody was back there to experience it.

AMAZING.

Okay. Brand new LNB, same problem. I tried switching the input cables on the LNB, but the problem persisted and didn't move to the other receiver. I did trace the line to the receiver with the problem and sure enough there is an inline amp about 60% of the way down the line from the dish. I'll take back the new LNB and try a barrell connector in place of the amp and see how it goes. Of course I have as million of those barrel connectors in my way when I don't need one and can't find one when I do. Have to go back to radio shack to return the LNB anyway so no biggie there.

I'll check back in once I try removing the amp. BTW: I think I understated the length of the run in my first post. After tracing it, it could be closer to 200'

Minor clarification. by "input cables on the LNB" I mean the coax to the receivers.

You have a bad power supply probably on the Philips reciever, or you are victom of the dreaded splitter in line between the Philips reciever and the LNB. My advice, take the new LNB back to the retailer and spend your money on a service call from Dtv for $70. Or call a local retailer and get a service call for as little as $35, depending on your area. Another point, if you don't have local channels, order them and get a triple lnb upgrade for free and perhaps a free reciever or two (that is depending on your area as well)

Those are all good ideas!

If you have checked the transponder signal levels and half of them are bad (the evens or the odds, I can't remember which), that could mean that the power supply is only sending 13 volts up the line and can't do the 18 needed for the other half.

I have heard, but not checked, that DirecTV have been feeling pretty swell with themselves lately and have quit making pretty much any deals, but it is worth a phone call! If you get someone to come out and do an upgrade, they will have to fix or replace the faulty stuff, and their install rates have been ridiculously low as long as you keep them out of the "custom" range of tasks.

Okay. Problem solved with a lot of help from you guys (Thanks Everyone). I took out the line amp that was about midway to the second receiver and the problem went away.

HOWEVER, the signal on the second receiver dropped from 90ish to 50-65ish (varies between even and odd transponders). I am getting a decent picture, but of course low signal strength might be a problem in bad weather. You guys think the line amp was faulty or just a bad idea in the first place?

I don't think the line amp was a bad idea because it did give you decent signal quality, but I still don't understand the problem. Go back and read the first post; there was some kind of interaction between the receivers that is not explained by just a bad amp.

You changed LNBs, so that is not likely the problem. I am stumped.

You still have a problem because a signal at 60 is likely to freeze, and bad weather will lower the signal even more.

The interaction you described is gone?

Did you ever just swap the location of the Sony and the Philips receiver? Remind me -- what happened with/to the problem?

Especially confusing is that the problem only occurred when someone was watching the Philips for a while, because the voltages on a satellite receiver are always going up to the LNB, whether it is on or off, watched or not! That is why I thought there might be some interaction between halves of the LNB.

But if removing the amp TOTALLY resolves symptoms, then the LNB is good and I am out of answers. Maybe you could put the amp back in place, but with a 3 to 6 dB satellite attenuator between it and the dish? This is a wild stab at getting the signal level back up but avoiding the problem.

Maybe it is worth calling DirecTV for some service, because 100 feet of wire should not drop the signal to 60 on any transponder. I don't know what they charge, but if it is a single charge to fix the problem no matter what, they will have to run it to ground and SOLVE it!

Do I understand correctly that you mean that the even are in the 90's and odd dropped down (or visa-versa)? If this is the case than I,m going to go out on a limb and suggest you check out as much of the line as possible, especially the connections. Too often I have found line spliced together when it should be a solid run. When these splices are outside, they often lack waterproof fittings and the center conductor is rusted clean through (amazed that they had any signal at all). I have also seen many cases of line being run outside on ground or low porch or deck in the same area as pets that chew everything they see and the result is a chewed up line in several locations. The same applies to the attack but with squarrels.

If nothing else, I still question that sony receiver. Is that the one that still has poor signal? Swapping the receiver locations should clue you in.