Entertainment Center: TVs, Stereos, VCRs and DVDs - heat from the systems

Hi,

I have just a standard tv stand for my 32" tv which houses my receiver and DVD player underneath (enclosed with a glass door).
I recently got digital cable and they put the box in there.
The tech who installed it made a offhand comment about the heat from the cable box set on the lower shelf on the DVD player. The receiver is on the upper shelf right above the cable box.

Well, this got me thinking if this was the best arrangement.
Should I be worried about the heat from the cable box damaging the DVD plaer or the receiver? Should I ever close the glass door?

I'm just not sure what is best. I've talked myself out of 3 different arrangments.

Thanks,
Shawn

doesn't the back of your tv stand have some big opening for wires and stuff? If so, then there should be sufficient airflow via convection to keep stuff somewhat cool. If not, you could simply cut a couple of small openings that can allow some ventilation (but don't compromise the stability of the cabinet)

You shouldn't worry too much about heat damage although technically speaking, MTBF drops by half for every 10C increase above room ambient if I'm not mistaken.

you could instead just leave the doors cracked open if nothing else....

Most commercial electronic parts are usually rated at 70C which is what I suspect is being used here. Provided the temperature on any of those parts do not rise above this you should be fine.

Not all parts can operate in free air and keep the temperature below the rated value. These are usually bolted on to heatsinks (some kind of metal chassis with fins) to help disspate heat.

If you are worried about this you can buy yourself a small thermometer (the kind the HVAC people use for servicing A/C equipment) and use it to check what the temp is inside the units. If it stays under about 50C you should be fine.

Does your cable box really get that hot? If it's not generating that much heat, I doubt you'll have a problem. If your existing components are surviving the current heat, the cable box probably will too.

I would put the biggest heat generator - the receiver - closest to the whatever venitilation you've got, with as much space above it as possible.

actually, going with common sense, you'd want to put the hottest component on top of everything else. That way you don't cook everything else above it :-)

But you don't want to put a heavy amp or receiver on top of a little dvd player or cable box if you can avoid it...

Adding to rav12's comment, 70C is a typical recommended maximum operating ambient temp. (some components have higher or lower ratings) There's also max junction temperature and power dissipation ratings, but that's a different discussion.

Keep in mind the 70C number is ambient inside the box and localized to the components in question...the difference between the ambient air in the room and the air inside the box can be significant if there's not much airflow.

This discussion seemed too brief to bring up things like junction temperature but now that it has been mentioned...

Junction temperature (Tj) is a transistor parameter and show how hot the transistor junctions can get. For a power transistor this can be around 150C. However, if it were to operate in free air the heat could build up to a lot more than this and to keep it cool it is usually bolted on to a heat sink (metal thing with fins - you may see it if you look inside your amp). The size of the heatsink is not guesswork but is carefully calculated using thermal resistance calculations. There may be some articles on the web for those interested.

Many integrated circuits operate at lower temperatures and the case usually cannot exceed something like 70C for commercial parts. You can also get more expensive parts for military applications for example. I cannot rememer the figures but 125C is one number for one of the categories. However, I doubt if any home appliances would be using military spec parts.