Looking for cause of dead TV and modem after thunderstorm

Thread Starter

Plowry87

Joined Oct 22, 2020
4
Good Morning,

I'm trying to identify the cause of some failed electronics after a thunderstorm Tuesday night. I happened to be in the living room when there was a lightning flash and thunder that shook the house. The power flickered and I heard a pop noise, it sounded like a half second of loud white noise. I assumed a surround sound speaker or something made the noise even though everything was powered off. Wednesday morning I find that the TV will no longer turn on, have tried a few outlets throughout the house. The comcast modem and cable/DVR box were also dead. I was able to get the modem to power up but the DVR box will not. I still don't have wifi, technician is coming tomorrow.

So, everything is plugged into the same surge protector except for the TV. Everything on that surge protector seems to be unaffected, accept the comcast equipment. The TV is plugged into its own surge protected recessed outlet (datacomm 45-0041-wh). The surge protector has not given me an audible alarm as it should when it has failed and it doesn't appear to be damaged. I have attached a rough schematic of how everything is wired. Can a power surge come through the coax and kill the comcast equipment? If so, I can't figure out what happened to the TV.

I should mention that several months ago, the Foscam camera unit in the schematic, lost it's ability to connect to the internet. It has an ethernet cord directly to the modem. The unit still works, just won't connect to the internet. I had an electrical engineer at work look it over and apparently the ethernet port is fried. So I potentially have had a ghost inside the electronics for a while.

Thank you for any help you can provide! I will be buying a new TV but I'm not comfortable plugging it in until I know what may have happened...
 

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Dodgydave

Joined Jun 22, 2012
9,666
Lighting usually hits the Aerial on the roof as it's the weakest point to earth, so in case of severe bad weather I unplug the aerial lead , if it does strike the TV , then it will take out the tuner and probably the PSU.
 

Thread Starter

Plowry87

Joined Oct 22, 2020
4
Lighting usually hits the Aerial on the roof as it's the weakest point to earth, so in case of severe bad weather I unplug the aerial lead , if it does strike the TV , then it will take out the tuner and probably the PSU.
My cable/internet comes in through buried RG11 cable. There is an access point at the ground by the road, then it is buried up to my house and then enters through the wall about 3' off ground.
 

DickCappels

Joined Aug 21, 2008
6,649
Is there a fuse in the damaged equipment? If one is blown that would suggest some particular circuits that need looking at. A blown fuse of a shorted rectifier could easily keep a TV from coming on.

Just because the cable TV signal comes into the house underground, that is not likely to keep high voltage from being induced from the magnetic field from a nearby lightning strike. The cable company should be well prepared to check for the cause.
 

Thread Starter

Plowry87

Joined Oct 22, 2020
4
Is there a fuse in the damaged equipment? If one is blown that would suggest some particular circuits that need looking at. A blown fuse of a shorted rectifier could easily keep a TV from coming on.

Just because the cable TV signal comes into the house underground, that is not likely to keep high voltage from being induced from the magnetic field from a nearby lightning strike. The cable company should be well prepared to check for the cause.
I will say I am a mechanical guy not an electrical guy, so I don't currently know much about the guts of the TV. Let's say a fuse is blown or a rectifier is shorted... My surge protector "should" have protected against whatever caused the short, right?

I hope the cable company can diagnose from that end, of course they won't be looking at the TV portion. My fear is they will say "yep, it's broken" and then throw in a new modem and call it a day.
 

upand_at_them

Joined May 15, 2010
545
fuses as in fuse/breaker panel for the house? or another fuse somewhere? No breakers tripped during the storm.
A fuse in the device. I fixed my neighbor's microwave some years ago, because the fuse inside had blown...and nobody would have known that there was one without removing the case.
 

DickCappels

Joined Aug 21, 2008
6,649
Your cable company's way of handling the problem is based on years of experience and their operating strategy. Don't worry -if the cable box goes again in the future, they will take care of it.

Let's say a fuse is blown or a rectifier is shorted... My surge protector "should" have protected against whatever caused the short, right?
One thing that learned when going through a problem with a product being destroyed by high voltage discharge is that there no sure fix, though you can come pretty close to making a product bullet-proof.

Our expectation is that your surge protector would have protected against whatever caused the short but in such circumstances hundreds or thousands of amps from a high voltage discharge can be fairly unpredictable and all we can do is repeat the experiment many times or accept the results known up until now.

When it comes to high voltage discharge you are at the mercy of many variales that may not be obvious
 

SamR

Joined Mar 19, 2019
2,789
There is no true protection from lightning but you can suppress the EMP effects of it. Surge suppression power strips for any "digital" or solid-state electronics is the quick fix. Whole house suppression at the main panel is better but does not fully protect from EMP induced into the interior wiring of the house. Both are better but nothing will protect you from a direct strike. It has been told that holding a 1 iron golf club over your head works because only God can hit a 1 iron. o_O
 
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