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Thread: Dodgy LNB?

  1. #21
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    Personally, I think you need a new mono-bloc but I don't think you need a new dish as they don't really deteriorate until there is heavy corrosion (sea air or similar) or they have been damaged by being hit with something (or swung past the dish E-W limits and hit a wall or something like that).

    Changing a mono-bloc is a LOT quicker, easier and cheaper than changing a dish, and you would still need a new LNB anyway even if the dish did prove in the end to be faulty - so change the LNB first and then see whether that has fixed the problem before going any further.

    PS: just looked again at the pics of your dish and it looks very like a very old 80cm perforated AMSTRAD SKY dish - and in pretty good overall condition (can't see any physical damage or corrosion). Just binned one of those but only because of the slightly bigger s/h dishes that I had collected over the years and am now setting up.

    Only problem I can see is that you may need to be careful in loosening the bolts holding the LNB to the arm because the original AMSTRAD plastic LNB holders get brittle after a long time - but I seem to see that this has already been replaced by something else. Anyway, spray some good quality penetrating fluid on all the bolts around the LNB a few days before you actually want to change it - and the bolts and screws should then come apart without too much problem.
    Last edited by jallen01; 17-03-2016 at 07:06 PM. Reason: Added the PS

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  3. #22
    V.I.P skomedal's Avatar
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    Quote Originally Posted by jallen01 View Post
    Personally, I think you need a new mono-bloc
    Question

    Why fit a mono-bloc to a motorised setup?

    Re. #1 "" It is connected to a motorised dish ""

  4. #23
    Member MysteryMan's Avatar
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    Quote Originally Posted by jallen01 View Post
    Personally, I think you need a new mono-bloc but I don't think you need a new dish as they don't really deteriorate until there is heavy corrosion (sea air or similar) or they have been damaged by being hit with something (or swung past the dish E-W limits and hit a wall or something like that).

    Changing a mono-bloc is a LOT quicker, easier and cheaper than changing a dish, and you would still need a new LNB anyway even if the dish did prove in the end to be faulty - so change the LNB first and then see whether that has fixed the problem before going any further
    Thanks for suggestion.

    Just to demonstrate my ignorance, what is the difference between a Mono-bloc and an LNB, please?

  5. #24
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    Quote Originally Posted by MysteryMan View Post
    Thanks for suggestion.

    Just to demonstrate my ignorance, what is the difference between a Mono-bloc and an LNB, please?
    A Mono-bloc IS a type of LNB but it is effectively 2 separate LNB tuners in a common housing, but with their "aiming" directions slightly off-set from one-another so that 2 separate satellites (e.g. 13E & 19E) can be received without the dish having to be swung - and with (IIRC) a 2-port mini-Diseqc switch inside it to allow the indoor receiver to select one or other satellite and thus allow that output to be fed down the single cable from the mono-bloc to that receiver.

    OTOH, a TWIN LNB also has two separate LNB tuners but they are both pointed in exactly the same direction and they have separate output F-connectors on the outside of the housing so that two (or more according to the receiver) channels on the same satellite can be received at the same time (just like two channels on SKY+)).
    Last edited by jallen01; 17-03-2016 at 07:32 PM.

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  7. #25
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    A monoblock is two LNB's, combined together, with one co-ax cable, going to your receiver. They come in different variances, 6 degrees, 3 degrees, etc, to allow you to view two satellites, e.g. 19.2E, and 13E.
    They are used on fixed dishes, not motorized, as your dish moves, to the selected satellite, rather than using Diseqc 1.1, to switch between satellites.
    A regular LNB just points at one satellite.
    If getting a new LNB, for your dish, I suggest getting a twin, 2 outputs, or a quad, 4 outputs, to allow you to run extra cables, in the future, either to a different room, or if you get a receiver with 2, or more, tuners.
    Attached Images Attached Images

  8. #26
    Super Moderator nml's Avatar
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    The Mono-bloc question has already been answered.This is not needed for a motorised system.
    The dish is an old offset so a normal LNB should br ok and on one of the pictures taken from the front the mounting pole looks vertical but from other angles it looks off this is normal only way to check is a spirit level and the motor looks like an old Stab motor.
    I think that most people these days use a 1mtr dish with a motor and a decent twin or quad LNB to allow for expansion.

    nml.




    Quote Originally Posted by MysteryMan View Post
    Thanks for suggestion.

    Just to demonstrate my ignorance, what is the difference between a Mono-bloc and an LNB, please?

  9. #27
    Member MysteryMan's Avatar
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    Thanks for all information.

    Now that the monobloc has been explained then, yes, that sounds familiar and was from a pre-motor incarnation when I was getting 13e & 19e.

    I've got a guy coming tomorrow, armed with new dish and LNB. I shall see if he will just try the LNB first and see if that works. If not, will replace both.

    I am pretty sure the mounting pole (the one fastened to wall) is aligned OK. The thing that I thought looked non-vertical was the arm of the motor that the dish is attached to - is that usual or should that be vertical on all satellites?

  10. #28
    Super Moderator nml's Avatar
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    It is normal caused by tracking the satellite arc.

    Quote Originally Posted by MysteryMan View Post
    Thanks for all information.
    I am pretty sure the mounting pole (the one fastened to wall) is aligned OK. The thing that I thought looked non-vertical was the arm of the motor that the dish is attached to - is that usual or should that be vertical on all satellites?

  11. #29
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    Quote Originally Posted by nml View Post
    It is normal caused by tracking the satellite arc.
    I was hoping someone would say that!!!!

    Thanks to everyone and I will report back after he's been tomorrow

  12. #30
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    Quote Originally Posted by MysteryMan View Post
    I've got a guy coming tomorrow, armed with new dish and LNB. I shall see if he will just try the LNB first and see if that works. If not, will replace both.
    As I said earlier, you, now he, will need to be very careful with the screws & bolts holding the existing mono-bloc - tell him that and, if possible, get up there beforehand and spray the penetrating fluid!

    OTOH, if something should "accidently" get broken, then he will probably say "can't fix that - you need the new dish" - and all that goes with it :-(

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  14. #31
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    Quote Originally Posted by nml View Post
    The dish is an old offset so a normal LNB should br ok

    I think that most people these days use a 1mtr dish with a motor and a decent twin or quad LNB to allow for expansion.

    nml.
    The Amstrad dish was a normal offset dish and the standard LNB holder took normal 40mm diameter body LNBs, and I agree that a twin or quad (albeit 4x LNBs in a quad - like a twin, but double the number of LNB tuners - is somewhat excessive for an installation with only one receiver) LNB should be perfectly adequate. Be careful what he wants to charge for the LNB itself as even a decent twin costs (much) less than 20!

    NB: If you still want to use the dish as a steerable one, the receiver has to be able to control the motor - any modern receiver will do that if the motor is Diseqc 1.2. compatible but very old motors use a different drive system that typically requires a 36Vdc supply and extra control lines, and very few modern receivers can do that without a special interface box. So if you still want reception from more than one satellite, then you need either a new mono-bloc for a couple of closely located sats such as 19E and 13E, or the correct combination of motor and receiver to drive a dish with a single/twin/quad LNB to point in the appropriate directions
    Last edited by jallen01; 17-03-2016 at 08:45 PM.

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  16. #32
    Super Moderator nml's Avatar
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    @ MysteryMan, Can you confirm which satellites you have been receiving untill you had this problem 2 or more?

  17. #33
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    Quote Originally Posted by nml View Post
    @ MysteryMan, Can you confirm which satellites you have been receiving untill you had this problem 2 or more?
    I could get all those between 0.8W and 28.2E, so 28.2E, 19.2E, 16E, 13E, 9E, 4.8E, 0.8W

    Can still get those, but, only V channels!

  18. #34
    Super Moderator nml's Avatar
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    Thanks, so to end the confusion.
    1. Your reciever is compatible with your motor, this was obvious.
    2. Your choices are new LNB or new LNB and dish, your choice you definately do not need a Monoblock, it might even be that your lnb skew adjustment is incorrect and a simple adjustment would fix.
    However I do think that for the cost of a new LNB it is worth it I don't think your old one will last much longer + if you have a twin or quad you can add other boxes for example bedroom or kids rooms all your choice.

    Good luck tomorrow.


    Quote Originally Posted by MysteryMan View Post
    I could get all those between 0.8W and 28.2E, so 28.2E, 19.2E, 16E, 13E, 9E, 4.8E, 0.8W

    Can still get those, but, only V channels!

  19. #35
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    Quote Originally Posted by MysteryMan View Post
    I could get all those between 0.8W and 28.2E, so 28.2E, 19.2E, 16E, 13E, 9E, 4.8E, 0.8W

    Can still get those, but, only V channels!
    FWIW, if your range is 0.8W & 28E and V only, then the LNB is almost certainly faulty (unless the receiver is failing to output the polarisation switching voltage element of LNB control - pretty unlikely!)

    However, that E-W range is low compared with what I would expect - which (in the UK) is roughly at least 30-40W to roughly the same 30-43E. Which is to say that either the LNB skew angle is incorrect as previously mentioned, and/or the dish is not correctly aimed at "your" True South (i.e. 0 degrees true, not magnetic, at the Greenwich meridian, as amended by your latitude E or W from that meridian) when at the nominal middle point of its E-W travel, and/ or the dish inclination on the steerable mount "pole" is incorrect - either too high or too low.

    Therefore, I think it is a combo of a faulty LNB (definitely), and (historically) slightly incorrect dish alignment in the initial installation. Solution to the first issue is easy/quick/cheap, whereas the solution to the second issue is more difficult because it relies on the experience and skill of the person doing the alignment (not done that for many years, so I now have another relearning task to master before I get that aspect right on my own replacement steerable dish!).

  20. #36
    V.I.P steviejb's Avatar
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    I am wondering, seeing as it's a monoblock LNB whether its possible to switch using diseq over to the other half of the LNB which might be working properly, so no need to call anyone out to replace the faulty part, this would of course mean changing all your sat settings to suit the changed position of the LNB, but you would have to do that anyway if you fit a standard LNB as the dish would need to point a few degrees left or right depending on which side was being used before and you would be using a center focus now

  21. #37
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    Steviejb

    FWIW, as the OP already has a guy coming to "fix" his dish/LNB, I think it's time for a new LNB, and relevant other adjustments, as the life of the existing one is likely to be distinctly limited in view of the obvious internal failure that has already happened.

  22. #38
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    Hi All,
    I don't want to put a "spanner in the works", but maybe something has been overlooked (or I missed something in the thread).
    Only V channels being received - yes, usually the LNB,
    BUT (hopefully not this)
    Could be the receiver not switching to 18 volts.

    Good luck.

  23. #39
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    Quote Originally Posted by DJSat79 View Post
    Hi All,
    I don't want to put a "spanner in the works", but maybe something has been overlooked (or I missed something in the thread).
    Only V channels being received - yes, usually the LNB,
    BUT (hopefully not this)
    Could be the receiver not switching to 18 volts.

    Good luck.
    Mentioned the 13/18V issue in Post 35, but no-one (else) commented on it.

  24. #40
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    Quote Originally Posted by jallen01 View Post
    Mentioned the 13/18V issue in Post 35, but no-one (else) commented on it.
    Because it is usually the LNB, and not the receiver, plus replacing the LNB is extremely cheap.
    Quite often we ask members to check their receiver, on another dish, even a fixed sky dish, but looking at the pictures, and the age, of the LNB, the odds are that the LNB has failed.
    I'm surprised an installer left a monobloc LNB, on a motorized dish, but it seems to have worked, for the user, has he got quite a few satellites, including 16E, and 4.8E, although he disn't mention 7E, 10E, and especially 23.5E.

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