Why on earth is this happening?

[HappyHippyDad]

A friend's partner has an interesting fault, if it is a fault.

She sets the shut down timer on the cooker and when the timer goes off (which in turn stops the oven from working), the TV screen in the other room turns black. This happened perhaps 2 times out 10 when trying to re-enact it.

The TV screen stays black for around 1 second and then resumes the programme as normal. I say black, rather than off as I'm not sure if it's losing power or not, as when it loses power (i.e. quick on off at the switch), it takes far longer than a second to resume. The TV is using the internet via a streaming box rather than an aerial.

The cooker and sockets are on separate circuits. They are both on the same RCD. I haven't been told of any other electrical items being affected, but this doesn't rule that out.

IR tests were all at least 25Mohms L/N - E.

Terminations in the consumer unit and at the oven switch were tight. I didn't get to the terminations in the cooker outlet plate or cooker itself.

Any ideas what may be going on?

 

[littlespark]

Only one answer.


Ghost!

 

[westward10]

I've had this before someone turned their kitchen light off which in turn did the same to the television. Sure there are other threads like this.

 

[SparkyChick]

I would hazard a guess as to this being a simple case of transient switching surges/brownouts. Some modern power supplies seem more susceptible to it than others. When I turn my main PC rig on/off it can trigger a blackout of one of my house mates monitors. Nothing else seems to trigger this behaviour and nothing else seems to be affected by it.

 

[HappyHippyDad]

I've had this before someone turned their kitchen light off which in turn did the same to the television. Sure there are other threads like this.

I shall have a hunt for them, thanks.

 

[HappyHippyDad]

I would hazard a guess as to this being a simple case of transient switching surges/brownouts. Some modern power supplies seem more susceptible to it than others. When I turn my main PC rig on/off it can trigger a blackout of one of my house mates monitors. Nothing else seems to trigger this behaviour and nothing else seems to be affected by it.

I haven't come across this before SC, so don't really understand it and this may be a silly question. Would surge protection help (if it is a transient switching surge}? I.e a simple surge protection plug that they could plug into the socket, and then the TV gets plugged in to that?

 

[SparkyChick]

I haven't come across this before SC, so don't really understand it and this may be a silly question. Would surge protection help (if it is a transient switching surge}? I.e a simple surge protection plug that they could plug into the socket, and then the TV gets plugged in to that?

It could do, but I'm just speculating based on my own experiences. PCs and the hardware associated with them can cause huge spikes... at my Mum and Dad's place I managed to weld several socket outlet switches closed using the inrush current when I turned various parts of my rig on.

I'm surmising that the oven is capable of producing a surge/dip of sufficient magnitude. The kind of symptoms you're seeing (loss of picture, but the monitor remains on) indicates the input/decoder board or possibly even the display itself is loosing power to such an extent that it's crashing (screen goes black) and then recovering (picture is restored). Of course if it's a smart TV then it could be the smart part of it that's crashing momentarily although I would expect that to be accompanied by a boot up time which usually includes some manufacturers logos which you would see.

How is that possible? If I were to take a punt, there are at present two primary voltages used for digital electronics. 5v and 3.3v. It's possible the controller uses both because some chips need 5v and some need 3.3v, some standards require you to use certain voltages.

It could be that this momentary interruption in supply adversely affects say the 3.3v rail because it has less smoothing capacitors on it than the 5v rail, or they've used a normal regulator rather than a low drop out version. LDO regulators have a much lower potential loss than their standard counterparts - to get a nice smooth stable 5v out of say a 7805 regulator, you're going to need to be feeding it with more than 5v, say something like 6v to 7.5v at least. LDO regulators might allow you to get away with say 3.5v for a 3.3v output. That's quite a difference, especially when you consider that what you're losing in voltage is going to be dissipated as heat. So, if your input voltage drops below that minimum regulation input voltage the output could do all sorts of weird things (they usually don't, they usually just drop off with the input voltage) and whatever is supplied by it could ultimately crash.

I'm guessing as to what exactly is happening, but this is the kind of thing that could be going on. A good quality surge arrestor may help prevent the issue and to be fair is probably the lowest cost option for a first stab at solving it.

 

[HappyHippyDad]

It could do, but I'm just speculating based on my own experiences. PCs and the hardware associated with them can cause huge spikes... at my Mum and Dad's place I managed to weld several socket outlet switches closed using the inrush current when I turned various parts of my rig on.

I'm surmising that the oven is capable of producing a surge/dip of sufficient magnitude. The kind of symptoms you're seeing (loss of picture, but the monitor remains on) indicates the input/decoder board or possibly even the display itself is loosing power to such an extent that it's crashing (screen goes black) and then recovering (picture is restored). Of course if it's a smart TV then it could be the smart part of it that's crashing momentarily although I would expect that to be accompanied by a boot up time which usually includes some manufacturers logos which you would see.

How is that possible? If I were to take a punt, there are at present two primary voltages used for digital electronics. 5v and 3.3v. It's possible the controller uses both because some chips need 5v and some need 3.3v, some standards require you to use certain voltages.

It could be that this momentary interruption in supply adversely affects say the 3.3v rail because it has less smoothing capacitors on it than the 5v rail, or they've used a normal regulator rather than a low drop out version. LDO regulators have a much lower potential loss than their standard counterparts - to get a nice smooth stable 5v out of say a 7805 regulator, you're going to need to be feeding it with more than 5v, say something like 6v to 7.5v at least. LDO regulators might allow you to get away with say 3.5v for a 3.3v output. That's quite a difference, especially when you consider that what you're losing in voltage is going to be dissipated as heat. So, if your input voltage drops below that minimum regulation input voltage the output could do all sorts of weird things (they usually don't, they usually just drop off with the input voltage) and whatever is supplied by it could ultimately crash.

I'm guessing as to what exactly is happening, but this is the kind of thing that could be going on. A good quality surge arrestor may help prevent the issue and to be fair is probably the lowest cost option for a first stab at solving it.

Thanks for such a detailed answer SC.

 

[timhoward]

I’d try a different input source with the Tv, even if you have to take a dvd player there, to pin it down to the streaming box or the TV itself.
I.E try and trigger the condition without using the streaming device.

It may also be worth watching the connection lights on the broadband router while it happens.

 

[Mikegh]

I've had this before someone turned their kitchen light off which in turn did the same to the television. Sure there are other threads like this.

I recall where a fluorescent capacitor would cause a separate socket RCD to trip when turning off the light