Another one to ponder

[trev]

I've been called out to a pub not far from me. The outside lights take the RCD out when it's lashing down. Simple IP problem, there's water getting in there sometimes. That one is fairly easy to sort out but there's another problem. When they turn them on the TV screens blank for a few seconds then fire back up, this happens 4 or 5 times then everything returns to normal.
At first thoughts I'm thinking RF interference but just now I'm at a loss to come up with a solution.
Opinions my learned friends please

 

[Pete999]

Are the lights causing a neutral to go open circuit for a instant during strike up of the outside light? a stab in the dark but sometimes it does happen

 

[trev]

I'd thought about that Pete but if it's only happening for an instant how come the TV screens cut out a few times over a few minutes?
I'm also unsure how I'd test for that, I could of course go round them all and check terminations. The OS lights are on a dedicated circuit btw. And they're halides

 

[Marvo]

Could be RF, maybe harmonics whilst the switchmodes stabilize or even a common or garden spike or noise. Are the TV's on the same ring/radial final circuit as the lights? How physically close are they as well?

I actually had a similar problem at a customer and I used a power smoothing PCB that I stripped from a microwave oven a few years ago and I squirreled it away for a rainy day. It worked a treat and I'm actually waiting for another similar filter PCB to become available for my house because when my borehole pump starts running it also causes my TV to lose picture for a few seconds. You also get similar filter boards in washing machines as well. If it's switchmode supplies on the lights you really need a filter with 4 x wound ferrite cores because hopefully this will cover both common and differential mode interference. I'll have a scratch around and see if I can fine you a schematic.

 

[Pete999]

I'd thought about that Pete but if it's only happening for an instant how come the TV screens cut out a few times over a few minutes?
I'm also unsure how I'd test for that, I could of course go round them all and check terminations. The OS lights are on a dedicated circuit btw. And they're halides

Disconnect them at the fittings so you have just the cables and switch the circuit on as if the lights are still connected see if that cures it, don;t know how many lights there are but if its happening a couple of times over a few minutes it could be the different start up sequences. other than that I'm lost as well

 

[Marvo]

Here's some general info, check out the first half of it because I would guess your issue is an EMC one rather than a RF one.

 

[trev]

There's 5 halides on 2 sides of the building. TVs are in the bar on the other 2 sides (it's detached btw) There's maybe a 12 metre square footprint.
The lights don't interfere with the TVs in the hotel rooms upstairs, it's just the ones in the bar which are on a separate circuit (as much as anything is on a separate circuit in an old pub in the UK lol)
If I'm honest the whole bloody place needs to be ripped to bits and started from scratch again but he's not going to do that, typical publican. Wants to turn an Austin Allegro into a Lamborghini but doesn't want to spend more than 20 pence.

 

[tazz]

Are the tv`s modern lcd/led with psu`s ...or old crt tv`s...?

 

[trev]

Flat screen LCD/LED with PSU

 

[ImpededLoop]

How do the tv's get their signal? I've experienced digital projectors in a lecture theatre behaving in a similar way when lights in the nearby corridor were switched on. Their signal was via CAT6 extenders. The IT people changed the extenders to a different manufacturer and it solved the problem.

 

[trev]

How do the tv's get their signal?

Not sure mate, I made the assumption that they're signal fed by coax/HDMI/?.....Either way I think that might have been a mistake.

 

[tazz]

Ok these switch mode psu`s have built in filters, and surge/spike protection....this is the action of one of the psu`s when hit by spike, they shut down to protect the tv.

 

[ImpededLoop]

Another thought, are all the tv's the same make and model?

 

[ImpededLoop]

Ok these switch mode psu`s have built in filters, and surge/spike protection....this is the action of one of the psu`s when hit by spike, they shut down to protect the tv.

I'd of thought that would put the tv's back into standby rather than a loss of picture for a few seconds.

 

[trev]

Another thought, are all the tv's the same make and model?

It's a fair sized building over 4 floors, cellar, bar, bedrooms and more bedrooms. I don't think there's any 2 things in there that are the same make and model. There's a board in the cellar that he wants replacing, it's covered in slug trails. No way I'm putting my hands on it without gloves