How hot does it get in there?

[mathog]

As I'm sure this forum's readers are painfully aware the typical LCD display puts all of its electronics inside what is essentially a narrow rectangular metal box with just a few holes on the top or back for ventilation. There is no fan, the only cooling is from convection, and from conduction through the box itself to the back of the display. This heat source lives within a narrow plastic case which itself tends to have only narrow slits for ventilation, and again, no active cooling. The back and top of an LCD display case tends to be warm to the touch, but not uncomfortably so, maybe around 110F.

Have any of you ever measured the temperature inside the inner metal box?
How hot was it?

Electrolytics do not like heat...

[PlainBill]

Re: How hot does it get in there?

That is an interesting question, and one which I had never checked. I'm using a 23" KDS wide screen monitor. The ventilation isn't very good in the area it sits. I just took a few measurements. Since this IS a scientific study, I will report the temperatures in Celsius.

My glass of ice water reads 0°C

The room temperature according to a thermometer about 3' away is 30°C

That same thermometer reports the outside temperature is 36°C

The air on the desktop is 30°C

The air above the case is 36°C.

The temperature just inside the top of the case is 35°C

With the probe contacting the shield around the electronics I read 44°C

Now I have to get a fresh glass of water.

For those Americans who still think in °F, the formula is (°C x 9/5) + 32 = °F

PlainBill

[mathog]

Re: How hot does it get in there?

With the probe contacting the shield around the electronics I read 44°C

Thanks for checking.

That gives us a lower limit for the temperature under the shield. I'm going to guess that the average air temperature inside is probably close to that, but a few spots could be a lot warmer. For instance, on the Viewsonic VX922 which is sitting open next to my desk at the moment on the PS board there is an L shaped heat sink with 3 pin voltage regulators (or power transistors?) bolted to it. This forms a sort of metal tunnel 2cm x 2cm x 7cm with the metal shield and the circuit board. Those active components are bolted to the inside of this tunnel, along with most of the (bloated) capacitors. There are holes in the shield right above it, but the total area of those holes is at most 1 square cm., so ventilation is pretty minimal.

[smason]

Re: How hot does it get in there?

Since this IS a scientific study, I will report the temperatures in Celsius.

Dude. My opinion of you (which was already very high) just went up a bunch more points.

I saw a map the other day which showed countries who haven't gone metric in red.
The U.S. and 2 tiny little specs somwhere else were the only red.

[PlainBill]

Re: How hot does it get in there?

Dude. My opinion of you (which was already very high) just went up a bunch more points.

I saw a map the other day which showed countries who haven't gone metric in red.
The U.S. and 2 tiny little specs somwhere else were the only red.

What can I say? There was a concerted push to switch to metric in the 70's. Manufacturing concerns were opposed because 'it would result in the US being flooded by cheaply made foreign products.'

Of course, since then they have been rushing to shut down their factories in the USA and switch production to foreign companies. Anything to obsolete old products and make a bigger profit. Now they are wondering why nobody can afford to buy their products.

PlainBill

[momaka]

Re: How hot does it get in there?

Have any of you ever measured the temperature inside the inner metal box?
How hot was it?

Never measured it, but I did perform a highly-scientific finger test on the heatsinks of a few LCDs . I think most run a lot hotter than 40C - probably closer to 50-60C. If the PCB has discoloration, I wouldn't be surprised if things got up to 70 or 80C, maybe even 90C. Sure would be nice if I actually had a thermometer to confirm this, though.

A few months ago I fixed a Daewoo L700C monitor for a friend of mine. Now that monitor is HOT! Literally.
Just within 5 minutes of use, the heatsinks were already unbearably hot. And after 10 minutes... no way you can even touch them without burning yourself. PCB underneath was discolored, of course. Then again, that's what you get for using linear regulators for pretty much all the rails.
And then if you think that's bad, the PSU board for this monitor has the caps right under the heatsinks (oh, and the caps were rated for 85C). They were Samxon GS, which are supposed to be blue in color - but half of mine were almost completely black due to heat damage.
If there's a hell for caps, this monitor has to be it.

[boomer400]

Re: How hot does it get in there?

Has anyone ever bothered to mount a small 12vdc cpu style fan in a chassis? where would you even put the power connections? I suppose it's easier for most people to just use a desktop fan and point it at the back of the monitor.

[Th3_uN1Qu3]

Re: How hot does it get in there?

All monitors have a 12v rail so if you really want to it's a no-brainer.

[showmemule]

Re: How hot does it get in there?

Yup had a 52 inch plasma I repaired bad caps go figure, but one thing I notice was the lack of heat dissapation parts. Soooo I installed a 4 inch computor fan in the back. 12 volt choices are pretty good in other monitors, and t.v's as well. Iam sure its money 1. They dont want the extra cost in the unit, and 2.they want it to burn up early, so as to get you to help them rotate there retail inventory, by buying another. Only problem you fix it instead.

[BarrelRoll]

Re: How hot does it get in there?

Interesting. I was working on a 50" SONY Plasma (Actually a Pioneer) and it had 5 fans in it, all with rotation sensors in case a fan stopped which would kill power to the set. The 42" SONY Plasmas (actually LG) didn't have anything IIRC.