My TV Cracks: Is It Heat or Discharge?

[DaveC426913]

I have had a number of TVs - both CRT and flat-screen - that make a loud crack occasionally.
It does sound just like appliance settling from heat expansion/contraction, but I'm not so sure that's what it is.

It cracks exactly once and only once, and does not seem to be correlated with heating up or cooling down. Last night it did this while still on.

Is there any possibility that it's not expansion/contraction? Is it possible it's some from of discharge? (That made more sense with older CRT devices - not so much with the new flat-screen devices.)

 

[berkeman]

Yeah, with CRTs you can get occasional "Tube Arcs", but I have no clue about what the flat screen TV is doing, Can you tell where it's coming from on the flat screen?

 

[DaveC426913]

Can you tell where it's coming from on the flat screen?

I'm not that patient.

 

[jedishrfu]

http://www.tomsguide.com/answers/id-2630414/make-clicking-popping-sound-coming-speakers.html

Opinions vary from relays to capacitor discharge to plastic heating up or cooling.

 

[rcgldr]

I still have two CRT monitors, a Hitachi CM 722 on a second older system, and my main monitor, a Viewsonic G225f (black). I've never heard a cracking sound from either monitor. The only sound I hear is the degaussing sound during power up.

 

[krater]

I think I'm familiar with what you're describing. I can think of a couple old CRT devices that displayed more of a propensity to do this than others. It's something I've really always chalked up to thermal effects on the components or case, like you said, "settling" like your house might when the sun goes down.

I'm not sure how detailed an explanation this could get while still covering a broad range of examples. If anything it's a phenomenon I've seen happen equally or more frequently when said device was powered on. Simple little things like a plastic bracket holding a circuit board that's injection molded into the case, and expansion and contraction cause slipping most times and occasionally it happens that it binds instead of slipping, eventually breaking loose and smacking into the back of the recess with an audible "CRACK".

Some old houses I've stayed in creak and settle more or less predictably under similar circumstances. Some make different noises every night. Of course this is all anecdotal from my personal experience.

I've heard loud popping noises through speakers but they have a different quality than what I think we're talking about.

 

[Greg Bernhardt]

My Samsung LCD does this. I always thought it was just normal thermal expansion.

 

[DaveC426913]

My Samsung LCD does this. I always thought it was just normal thermal expansion.

Yeah, It is the most mundane explanation. It's just the strange timing that's making me suspicious.
You'd think that thermal expansion/contraction would be closely tied to powering up and down.

 

[Fervent Freyja]

Any gas heat sources happen to be nearby? Is it mounted to the wall? Mine makes similar noises, the bracket is holding its maximum load, those are the only causes for it that I can reckon. Some of these tvs are too heavy and poorly supported, try stomping into the room to see if floor vibrations are triggering some loose support or structural components to move- that can cause an one-time noise in many things.

 

[DaveC426913]

Any gas heat sources happen to be nearby?

Other than me? No.

Is it mounted to the wall?

No. None of them are/were.

 

[Evo]

My tv does this all of the time, usually in the middle of the night when it's been off for awhile, I always thought it was just static discharge

 

[meBigGuy]

When you say flat screen, it doesn't mean much. Do you mean LCD, or Plasma, or flat face CRT. If it is LCD, is it LED backlight, or CCFL. (CCFL is high voltage)

CRT based systems will arc ocasionally, especially after years of gathering dust. Open it up and blow out the dust. Same for the flat screen (actually, you might just try blowing out the dust through the vent holes.

 

[DaveC426913]

When you say flat screen, it doesn't mean much. Do you mean LCD, or Plasma, or flat face CRT. If it is LCD, is it LED backlight, or CCFL. (CCFL is high voltage)

Exactly. I'm not sure which type(s) it/they is/are. I aim was to merely distinguish them from CRTs - i.e. no high voltage tube.

CRT based systems will arc ocasionally, especially after years of gathering dust. Open it up and blow out the dust. Same for the flat screen (actually, you might just try blowing out the dust through the vent holes.

Now that I think about it - surely if it were any kind of electric arc, I would see a disruption - even infinitesimally - on the screen. There is no disruption at all.
That points toward a purely physical phenom rather than any electrical phenom.

 

[rbelli1]

no high voltage tube.

Many flat screen TV's have high voltage tubes either the fluorescent back-light or in the plasma display.

More modern LCD's use LED's.

BoB

 

[newjerseyrunner]

A static electrical discharge shouldn't affect an LCD screen, especially if it's in the power supply. If you can determine an approximate location of the crack, you could look up the internal structure online and figure out where it's coming from. My bet would be the power supply, but if you're sure that it's a mechanical sound and not electrical, it may just indicate something expanding from heat and readjusting itself. Thermal expansion / contraction may not be directly correlated to boot up/down. Most of the heat should go to the heat sink.

 

[Baluncore]

If the crack is a reseating of materials due to differential thermal expansion, then you should be able to trigger the release of the stored energy by taking hold of the top two corners, when convenient, and twisting it slightly. Physics is an experimental science.
If it makes the crack when the case is twisted, it is probably a stiction between parts or the plastic case.

 

[Yomac]

My tv does this! It just happened and I wanted to resurrect this post. I've come to conclusion that it the case of the tv releasing trapped heat inside of the case because it only does it once and while it has been on for 2 hours or so. I can't believe I found this thread lol. Sorry I'm late.