Multiplex Information

[Matthew]

We're on a IRS and yesterday I noted 1 mux was down (indicated in the box menu) yet the diag entry did not reflect that, today there are 2 mux down and the diag entry remains the same!

When does the entry update itself?

It would be useful so I could show the engineer when he comes especially if a history can be shown as often these issues are due to water ingress and when they come in the dry they've got better (its raining now)!

 

[Black Hole]

All the report on the diagnostics page presents is the data gathered by the Humax firmware at the time of retune. If you want to update the data, you need to run a retune.

The only way to get live data (without potentially corrupting your tuning database) is to run the signal test via the Humax menus: Menu >> Settings >> System >> Signal Detection.

 

[Matthew]

Thanks BH.

The 'engineer' did eventually come, said the loss of the mux in the rain was just due to signal deterioration due to the rain! What rubbish. He did fiddle with the system aerial to improve things but said he couldn't get it better as the signal in the area was very poor quality.

Later that day his changes meant we lost the HD mux!

So I though sod it I`ll put up my own aerial. When I did so and measured the signal I found quality is absolutely fine, just the level is low, but still adequate for digital even with just a 4 element array. So his report of poor quality is due to the kit they are using and he was unable/unwilling to diagnose that. I'm appalled and the standard of work some are happy to provide these days .

When I was messing around connecting and disconnecting the aerial feed the T2 suddenly crashed immediately after a signal restoration (the display weant to digital noise then off and the box was completely unresponsive), is the T2 system disturbed by such events? There is no entry in the crash log.

 

[Black Hole]

There is no entry in the crash log.

If the system freezes, how can it write to the crash log? Yes, anything Humax didn't test for in software development can crash it.

 

[MikeSh]

When I was messing around connecting and disconnecting the aerial feed the T2 suddenly crashed immediately after a signal restoration (the display weant to digital noise then off and the box was completely unresponsive), is the T2 system disturbed by such events?

The Humax manual does say to disconnect the power before connecting the aerial.

 

[Matthew]

The Humax manual does say to disconnect the power before connecting the aerial.

Isn't that placed there just out of safety concerns, TV's of old often had the aerial socket at half mains potential due to power supply design and all aerials are subject to lightning strikes, especially if placed within an attic for some reason.

 

[EEPhil]

I'm sure I could be talking blx - I can't immediately find a reference that confirms this. I know I've managed to get a static type shock from a TV aerial (no amplifiers involved). I also have a vague recollection of the potential at roof level being different to that at ground level (earth) - causing the shock when you earth the aerial (to yourself or the Humax). If I can get a shock, your poor Humax can. The shock can't be enough to fry the chips - but it may be enough to corrupt the data signals causing a crash. Therefore, probably not just safety concerns.

 

[Matthew]

I know I've managed to get a static type shock from a TV aerial

Its not static, by regulation TV power supply's must be split to a live side and a output side such that there is no direct connection between the 2, this is normally done through transformer action. This means in the absence of an earth to the output side it will 'float' at half mains. Signal amplifiers typically use 12V power supplies, if a mast head amp is used 12V or similar is fed via the feed cable.

If you touch a floating aerial socket you will get a shock, but the isolation means it is not lethal. In a IRS by regulation the kit must be bonded and earthed meaning the system will provide an earth on connection of the aerial, this can mean a visible spark may be seen when connected.

 

[Trev]

@Matthew. If you get it off the end of an aerial feeder, it certainly IS static. If you touch either side of a floating power supply, you will not get a shock as there is no circuit made to the other side, which there must be to allow current to flow and give you a shock (no current = no shock). You will merely reference the side you touched to whatever potential you are at, often earth.
If you get a lightning strike on the aerial just as you connect/disconnect, it won't matter whether the set was switched on or off or not, you will likely die.

@EEPhil The static potential, if it gives you a shock is likely to be several kV and certainly more than enough to "fry chips" (of the electronic variety).

 

[EEPhil]

If you get it off the end of an aerial feeder

That was what I meant - perhaps it wasn't clear.

The static potential, if it gives you a shock is likely to be several kV and certainly more than enough to "fry chips" (of the electronic variety).

Which begs the question - why doesn't it? And what is the real reason for suggesting you turn the power off when fiddling with the aerial? (Both rhetorical - maybe)

 

[Trev]

It does, that's why it is best to use an earthed pad and wrist band when handling electronic components, especially CMOS ones.
I suspect the 'power off' goes back to the 'olden days' when the chassis could have a voltage , referenced to earth on them?
But having said that, I have heard rumours of connecting sat feeders to the box with power on has been known to fry the LNB, but it has not happened to me (yet) whilst poking around with my dish set up.

 

[MikeSh]

Which begs the question - why doesn't it? And what is the real reason for suggesting you turn the power off when fiddling with the aerial?

When everything is connected together then static doesn't build up. When a conductor is isolated from the system (such as a disconnected aerial) static may build up on it or at least a potential may develop between the two parts. When touched back to the system it rebalances with a sudden flow of current. Pop.
It is never a good idea to connect/disconnect sensitive circuitry while the system is powered up.

 

[EEPhil]

It's never a good idea to touch the metallic parts of the aerial connector either. But that didn't stop me doing it by accident. Ouch!

 

[Matthew]

but it has not happened to me (yet) whilst poking around with my dish set up

I used to install IRS, I've connected many sat receivers live, its not a problem.

I did come across a customers set where the voltage on the aerial socket gave a really nasty bite, clearly not a well designed TV in that case, in that install we were combining LAN and feeds on the same plate, the current from the set was so bad it stopped the lan working! We had to put an isolator on the aerial feed to resolve.