LNB failure modes

I am doing a long distance diagnosis on a freesat system that I
installed a year or so ago.

Symptoms are that when the sat box is first powered up, the picture is
unreliable with blocking or reports of no signal but later on the
picture will recover and programmes can be viewed normally without
interruptions.

LNB is a quad, first box is a Humax Foxsat with 2 feeds, second box on
third feed shows same symptoms when fault is manifesting on box 1.

To top it off, leaving box 1 on all the time solves the problem.

I'm guessing the LNB is duff and that this failure mode has been
mentioned here before but would welcome opinions. I can of course buy a
new LNB to take down anyway but I'd prefer to save the cash for the old
bird if I can.

Nobody has been in a position to ding the dish so I'm guessing the LNB
is a more likely bet than aim.
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********

fred wrote:
I am doing a long distance diagnosis on a freesat system that I
installed a year or so ago.

Symptoms are that when the sat box is first powered up, the picture is
unreliable with blocking or reports of no signal but later on the
picture will recover and programmes can be viewed normally without
interruptions.

LNB is a quad, first box is a Humax Foxsat with 2 feeds, second box on
third feed shows same symptoms when fault is manifesting on box 1.

To top it off, leaving box 1 on all the time solves the problem.

I'm guessing the LNB is duff and that this failure mode has been
mentioned here before but would welcome opinions. I can of course buy a
new LNB to take down anyway but I'd prefer to save the cash for the old
bird if I can.

Nobody has been in a position to ding the dish so I'm guessing the LNB
is a more likely bet than aim.

LNBs do tend to fail when there's hot weather.

Bill

In article , Bill Wright
writes
fred wrote:
I am doing a long distance diagnosis on a freesat system that I
installed a year or so ago.

Symptoms are that when the sat box is first powered up, the picture is
unreliable with blocking or reports of no signal but later on the
picture will recover and programmes can be viewed normally without
interruptions.

LNB is a quad, first box is a Humax Foxsat with 2 feeds, second box on
third feed shows same symptoms when fault is manifesting on box 1.

To top it off, leaving box 1 on all the time solves the problem.

I'm guessing the LNB is duff and that this failure mode has been
mentioned here before but would welcome opinions. I can of course buy a
new LNB to take down anyway but I'd prefer to save the cash for the old
bird if I can.

Nobody has been in a position to ding the dish so I'm guessing the LNB
is a more likely bet than aim.

LNBs do tend to fail when there's hot weather.

But this is Scotland ;-)
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********

fred wrote:
In article , Bill Wright
writes
fred wrote:
I am doing a long distance diagnosis on a freesat system that I
installed a year or so ago.

Symptoms are that when the sat box is first powered up, the picture is
unreliable with blocking or reports of no signal but later on the
picture will recover and programmes can be viewed normally without
interruptions.

LNB is a quad, first box is a Humax Foxsat with 2 feeds, second box on
third feed shows same symptoms when fault is manifesting on box 1.

To top it off, leaving box 1 on all the time solves the problem.

I'm guessing the LNB is duff and that this failure mode has been
mentioned here before but would welcome opinions. I can of course buy a
new LNB to take down anyway but I'd prefer to save the cash for the old
bird if I can.

Nobody has been in a position to ding the dish so I'm guessing the LNB
is a more likely bet than aim.

LNBs do tend to fail when there's hot weather.

But this is Scotland ;-)
Oh I see. Well they also tend to fail when rain gets inside them.

Bill

Am 12.07.2011 12:45, schrieb fred:
I am doing a long distance diagnosis on a freesat system that I
installed a year or so ago.

Symptoms are that when the sat box is first powered up, the picture is
unreliable with blocking or reports of no signal but later on the
picture will recover and programmes can be viewed normally without
interruptions.

LNB is a quad, first box is a Humax Foxsat with 2 feeds, second box on
third feed shows same symptoms when fault is manifesting on box 1.

To top it off, leaving box 1 on all the time solves the problem.

I'm guessing the LNB is duff and that this failure mode has been
mentioned here before but would welcome opinions. I can of course buy a
new LNB to take down anyway but I'd prefer to save the cash for the old
bird if I can.

Nobody has been in a position to ding the dish so I'm guessing the LNB
is a more likely bet than aim.

Though not a problem exclusive to LNB's this sounds like a component in
the LNB which has a problem until it warms up. As slong as it's kept
under power it's OK but when it's switched off and cools down you get
the problem again at switch-on. This type of problem usually gets worse
until the component fails altoghether.

Ian

Bill Wright wrote:

Oh I see. Well they also tend to fail when rain gets inside them.

Bill

Hijacking this thread, both our Sky boxes have suddenly begun reporting
'There is a technical fault with this channel', every few days and
require powering down to reboot. These failures aren't simultaneous but
seemingly random. They use two ports of a quad LNB. Is that the likely
problem?

Cheers
Andy C

"fred" wrote in message ...
I am doing a long distance diagnosis on a freesat system that I installed a year or so ago.

Symptoms are that when the sat box is first powered up, the picture is unreliable with blocking or reports of no signal but later
on the picture will recover and programmes can be viewed normally without interruptions.

LNB is a quad, first box is a Humax Foxsat with 2 feeds, second box on third feed shows same symptoms when fault is manifesting on
box 1.

To top it off, leaving box 1 on all the time solves the problem.

I'm guessing the LNB is duff and that this failure mode has been mentioned here before but would welcome opinions. I can of course
buy a new LNB to take down anyway but I'd prefer to save the cash for the old bird if I can.

Nobody has been in a position to ding the dish so I'm guessing the LNB is a more likely bet than aim.
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********

I am not at all convinced it's the LNB, it could be the Humax PSU that is
causing the problem.

My experience in using two Philips quads to supply 8 feeds to a workshop
showed that a given element of a quad LNB was not immune to disturbances
in the power fed to its neighbouring elements. In fact, powering down a box could
make one or more of the other feeds momentarily glitch.

Why can't they have the Humax powered 24/7, or is that to simple a solution?


--
Graham.

%Profound_observation%

In article , Graham. writes

I am not at all convinced it's the LNB, it could be the Humax PSU that is
causing the problem.

My experience in using two Philips quads to supply 8 feeds to a workshop
showed that a given element of a quad LNB was not immune to disturbances
in the power fed to its neighbouring elements. In fact, powering down a box could
make one or more of the other feeds momentarily glitch.

Yes, I can see that might be a possibility. Now, what's an easy way to
tap off a monitoring point from the sat coax to measure on a multimeter?
Would a few turns through a ferrite bead be enough to block the RF and
still maintain the signal to the receiver?

Why can't they have the Humax powered 24/7, or is that to simple a solution?

I prefer fixes to workarounds ;-). Chances are it would work for a while
then fall on its arse eventually so I'd prefer to do it properly. She
finally has freeview via a relay so I will add that as a backup on my
next visit but it is only the PSB muxes.

I might just get a spare quad LNB anyway in case it is that and if not
it will be a handy item for my toolkit, it's only a few quid after all.
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********

In article , Bill Wright
writes
fred wrote:
In article , Bill Wright
writes
fred wrote:
I am doing a long distance diagnosis on a freesat system that I
installed a year or so ago.

Symptoms are that when the sat box is first powered up, the picture is
unreliable with blocking or reports of no signal but later on the
picture will recover and programmes can be viewed normally without
interruptions.

LNB is a quad, first box is a Humax Foxsat with 2 feeds, second box on
third feed shows same symptoms when fault is manifesting on box 1.

To top it off, leaving box 1 on all the time solves the problem.

I'm guessing the LNB is duff and that this failure mode has been
mentioned here before but would welcome opinions. I can of course buy a
new LNB to take down anyway but I'd prefer to save the cash for the old
bird if I can.

Nobody has been in a position to ding the dish so I'm guessing the LNB
is a more likely bet than aim.

LNBs do tend to fail when there's hot weather.

But this is Scotland ;-)

Oh I see. Well they also tend to fail when rain gets inside them.

Point taken, "it's either that or it isn't" is a good approach, I'll
shell out for a spare LNB and take it down in case it's needed.
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********

fred wrote:

LNBs do tend to fail when there's hot weather.

But this is Scotland ;-)

Oh I see. Well they also tend to fail when rain gets inside them.

Point taken, "it's either that or it isn't" is a good approach,

It's the only possible approach when discussing a fault remotely,
without the ability to carry out tests.

These faults can be so weird and unpredictable. Last week I had a
satellite IF splitter that developed an internal DC short circuit after
a month without problems. On site the fault was consistent and solid. I
took the item off the board, scrutinised its connectors minutely, tapped
it on the wall, turned it upside down, said a magic spell over it, and
it continued to be faulty. Back home I decided to investigate it so I
checked for the DC short as a preliminary to prizing the lid off. The
short wasn't there and the unit worked perfectly. Again I tapped it on
the wall, turned it upside down, said a magic spell over it, yet it
continued to work perfectly.

Also last week I had complaints of one channel going off and 'flashes of
interference' on some of the satellite channels on an hotel system. The
sat channels are carried as analogue TV signals. I went out and the
fault wasn't there, next day they rung back, I went out, the fault
wasn't there, two days later they rung back, I went out, the fault
wasn't there. I stood looking at the head end wondering what to do when
the display on one of the modulators came on, by itself, and the unit
started climbing up through the channels, momentarily wiping out the
modulator outputs that were on close channels* as it did so. The 'up'
button on the modulator was occasionally intermittently making contact
when it shouldn't have been. Isn't that a bugger?

*Channel filters prevented it affecting more distant channels.

Bill