black screen when fridge motor or heater starts

It could be that a little burst of ElectroMagnetic Interference is affecting the connection between the PC and TV. I suspect it might actually be the TV blanking out as it sees a spike in the signal and needs to work out what standard to apply after the interference has stopped and the intelligible signal reappears.
You may have some luck if you add an interference supressor adapter or socket strip to the PC/ TV combo. I'm assuming the TV and PC are plugged into the same socket? If not, try that.

Edit: What's the connection protocol between PC and TV? HDMI?
Is the cable as short as it can be?
Has the cable got ferrite beads on it (tubular plastic lumps on the cable behind the plugs!)

Also worth thinking about a suppressor for the freezer etc.

I'm not well versed in what's available, but this sort of thing might help:

I suspect it's not so much a surge protector you need as an EMI filter.

This may or may not relate to the interference - It does raise the question of whether the earthing arrangements in your apartment are OK. Has there been an electrical inspection in recent years?

That it happens only when PC is plugged in it strongly suggests EMI and not due to a drop in supply voltage from the motor kicking in.

That would still be odd, as most items these days are reasonably tolerant, but it might be an indication that somehow the socket earths for PC and TV are going to different voltages during the surge and that is flowing on the cable between them.

As a first check I would go with @Avo Mk8 and try with PC and TV plugged in to the same distribution block or socket pair. If that stops it, then it looks like it is related to the earth loop.

However, that in itself may be an indicator of bigger problems in the wiring, but not necessarily so. Getting an electrician in to test it might be worth considering, or trying a good quality socket tester such as this on the two normal locations you have TV & PC plugged in:

Does your flat have an EICR (electrical installation condition report) that is recent?

I'm overthinking this !!
I imagine your TV has no earth connection - probably just on a twin flex.
Are there other things plugged into the TV?
If there are, you might try disconnecting everything else, including the aerial, LAN etc, but leave the PC connected, and see if it still blanks out!

Avo Mk8 said:

Are there other things plugged into the TV?
If there are, you might try disconnecting everything else, including the aerial, LAN etc, but leave the PC connected, and see if it still blanks out!

Click to expand...

Very good point! Trying all attached devices from the same multi-way block might help.

TV antenna normally won't cause issues and often is isolated, but one should never rule things out if the above makes no difference.

I agree with the above, that it is likely to be interference momentarily corrupting the HDMI or DVI connection from computer to TV. This is actually quite a common problem and is unlikely to be harmful to either device although it is very annoying.

Do you have another HDMI cable to test with? If the one you are using came free with something, it might be of low quality and not well shielded against interference. Contrary to some claims, better quality HDMI cables don't give better pictures but they are more likely to be resistant to interference.

If a better / different cable doesn't solve the problem, do you have another monitor you can display the PC output on, that might prove that it is specifically this pairing of PC and TV that is susceptible?

BTW how long is the cable? Is it just a single cable with no inline extensions / adaptors?

Thanks for the replies everyone. I've attached 3 photos showing the connections if this helps and it shows how far the PC tower is from the TV.

The photo showing the back of the PC and the 4 socket extension lead has plugs connected to the TV, Blu-ray player and speaker bar.

The power leads for the TV and PC will not reach a main socket on the wall so I have to use and extension lead by the way, not sure if that makes much difference?

The HDMI cable that I currently have was one that came with the TV so it's not of high quality. The last one I had was decent but it broke. I can't remember if the problem was happening then also or after I used the cheap HDMI cable. The silver HDMI cable you see plugged into the side of the TV is connected to my Blu-ray player which is of high quality as I thought this may improve image quality when watching films.

What's the connection protocol between PC and TV? HDMI? Yes it's a HDMI cable connected to the TV from the PC.

Has the cable got ferrite beads on it (tubular plastic lumps on the cable behind the plugs!) No there are no ferrite beads on the hdmi cable (I looked up ferrite beads on google so I know what you mean)

Yes I may replace the 4 socket extension lead with a surge protector one like in the amazon link.

I'll try what you have suggested and will let you know.

Many thanks
Jo

jolb72 said:

The power leads for the TV and PC will not reach a main socket on the wall so I have to use and extension lead by the way, not sure if that makes much difference?

Click to expand...

No, that should not matter here. Having them all together already suggests it is nothing to do with the flat's fixed wiring.

jolb72 said:

The HDMI cable that I currently have was one that came with the TV so it's not of high quality. The last one I had was decent but it broke. I can't remember if the problem was happening then also or after I used the cheap HDMI cable. The silver HDMI cable you see plugged into the side of the TV is connected to my Blu-ray player which is of high quality as I thought this may improve image quality when watching films.

What's the connection protocol between PC and TV? HDMI? Yes it's a HDMI cable connected to the TV from the PC.

Has the cable got ferrite beads on it (tubular plastic lumps on the cable behind the plugs!) No there are no ferrite beads on the hdmi cable (I looked up ferrite beads on google so I know what you mean)

Click to expand...

Certainly it would make sense to try a new and better quality HDMI cable.

Some of the typical shops have stupid prices for them, but equally some of the dubious sellers on eBay, amazon, etc, are pedalling rubbish.

Something like this might be good value:

You can buy separate clip-on ferrites to add to the cable in case there is some issue with the TV and/or PC ends being more sensitive. Ideally one at each end of the HDMI cable:

I reckon the problem is to do with the voltage dip whenever there is a short surge in current as when the fridge starts or large load like the heater turns on. If your TV, computer, fridge and heater are all on one socket circuit, which may well be so in a small flat, then the voltage dip will be detected more readily by the computer.

Most computer will monitor the power supply to confirm it is providing the correct voltage. If the computer detects the voltage is falling it will attempt to conserve power by shutting down certain activities like outputs and use what energy it has stored in its capacitors to quickly shut down in a safe way preserving as much key data as possible. If the power returns to normal within a short time the computer will detect this and return to its activity just before the voltage dip but this will take a few seconds to do. (For the technically minded, the voltage dip is made worse in most computers using switched mode power supplies because with a falling input mains voltage they draw more current to compensate). Of course it could also be there is a problem with the computer power supply but we can come to that later.

To help me could you:

1. Show me a picture of the consumer unit (fuse box) with its lid open;

2. The circuit breaker switches or fuses should be labelled with their purpose; how many are labelled for 'sockets'?

3. Do the lights noticeably dim briefly when the fridge starts or heater turns on? You may need to swap one led or fluorescent lamp for an older filament lamp which would show the dimming more starkly.

3. If you have two (or more labelled sockets) could you turn one and only one off in turn and then check to see if the fridge and the TV are both without power which would indicate they are on the same socket circuit. Only do this if you have circuit breakers with switch controls. See my electrical art attached which shows two daisy chains of socket each fed by their own fuse/circuit breaker.

4. If they are on the same socket circuit and there is at least one other socket circuit, either relocate your computer and TV near a socket of this other circuit or buy yourself an extension lead and use it to temporarily power the TV and CPU from this other socket circuit. When the fridge or heater turn on does the screen now go blank?

Perhaps best do this step by step if it helps starting with with 1 and 2 above.

This is the extension lead you will need available from most hardware and electrical shops and sometimes supermarkets. or buy one from Amazon like this one obviously of a suitable length:

I am not sure that the extension-lead-to-another-circuit test will conclusively distinguish between voltage brownout and interference. Moving the supply for the monitor and TV to a point where it shares less common impedance with the fridge / heater is likely to reduce the amplitude of any transients reaching the mains leads and PSUs that might be coupling into the signal circuit. So we might find that it 'solves' the problem without indicating what the problem was and therefore how to solve it permanently.

It is also hard to see how a heater plugged into an intact circuit could cause a brownout sufficient to affect anything. The element resistance is lower when cold but not much lower, so a 5% circuit VD might become 10% momentarily, not enough to disrupt a normally-functioning SMPSU.

Hi lolb72
A quick thought after seeing your photo's.
It would be worth swapping the HDMI cable you are using for the Blu-ray player, for the PC one.
Or as a quick test, just take that lead out of the Blu-ray and put in in the PC, to see it it changes the situation at all.
I suspect the ferrites might be a red herring - in my limited experience they seem more to do with getting equipment to pass EMC tests (emissions?), and I fear their effect may be too subtle to help here.

I'd pin my hopes on a socket strip with an EMI filter.
Or go the whole way and invest in a UPS, which would also tackle any voltage dip issue as described by marconi.

I don't know the reason for this but about five years ago I was working in someone's flat and they said switching the fluorescent light on in the kitchen pinged off the TV and Sky box, I tried it and sure enough it did. They had table lamps in the kitchen and had stopped switching on the main light.

westward10 said:

I don't know the reason for this but about five years ago I was working in someone's flat and they said switching the fluorescent light on in the kitchen pinged off the TV and Sky box, I tried it and sure enough it did. They had table lamps in the kitchen and had stopped switching on the main light.

Click to expand...

About 1996 I got an ESD test gun and, obviously, the first thing I did was wind it up to its maximum of 18kV and try discharging it on the chassis of my office PC. It was fine but minutes later the guy in the next office came in angered by his crashing and needing to power off and back on again to get his mouse working.

I was told in no uncertain terms not to use it again in that area!

As @Avo Mk8 suggests, try an HDMI cable swap first to see if it makes any difference. If so then maybe buy a better one and possible a few of the ferrites to help it (and any older HDMI cables).

Next cheapest would be to get a power block with a EMI filter / surge protection in it and see if that fixes it.

A UPS is a pretty expensive option, though at least you could watch TV for a few tens of minutes more if there is a power cut...

Lucien Nunes said:

I am not sure that the extension-lead-to-another-circuit test will conclusively distinguish between voltage brownout and interference. Moving the supply for the monitor and TV to a point where it shares less common impedance with the fridge / heater is likely to reduce the amplitude of any transients reaching the mains leads and PSUs that might be coupling into the signal circuit. So we might find that it 'solves' the problem without indicating what the problem was and therefore how to solve it permanently.

It is also hard to see how a heater plugged into an intact circuit could cause a brownout sufficient to affect anything. The element resistance is lower when cold but not much lower, so a 5% circuit VD might become 10% momentarily, not enough to disrupt a normally-functioning SMPSU.

Click to expand...

My starting hypothesis for analysis of this problem is there may be a defect in the wiring along the lines of what littlespark shows in #5790 of the thread 'Dodgy trade pictures for your amusement' - a connection or connections within or without the flat which is/are not made satisfactorily the effect of which becomes/become manifest during high current events.

The OP says a fridge starting or a heater starting causes the problem - these appliances have different inrush current characteristics but one thing in common - a large current - the former briefly and the latter longer term and roughly of the same magnitude - and yet they cause the same effect - the brief blanking of the TV screen when used a monitor for the CPU

So for me there is something about the reaction to and recovery from these switch on events (note not switch off) which I reckon is taking place within the CPU/PC - it only happens when I am working on my PC - which is causing the problem - the stress of a poor connection like littlespark illustrated during switch on of the fridge or heater.

Postscript: Electrical contact theory, A-spot, electrical contact resistance, electron ballistic conduction, Sharvin resistance, Ragner Holm on contact conduction see:

Electrical contacts - Wikipedia - https://en.wikipedia.org/wiki/Electrical_contacts