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#97995 - 04/10/18 03:32 AM Re: 976 is warm [Re: Owl's_Warder]
EEman Offline
Desperado

Registered: 11/11/09
Posts: 482
Loc: Canton, MI
Let's break it down.
Heat rises (at least on earth).
Heat is transferred by conduction, convection and radiation.
Heat flows from hot to cold.
Everything resists this flow.

What we are really concerned about is something called the Junction Temperature in the chips in our electronics. The junction is where the heat is actually generated. In order for us to feel the heat it must first flow through "stuff".

e.g. my 7075 (simplified)
transistor junction -> transistor case: Conduction
case -> heat sink: Conduction
heat sink -> air: Convection

Think of each of the "->" as a pipe which heat travels through. Each interface will only let so much heat through. This is called the thermal resistance of the interface.

Metal to metal conduction is pretty efficient at transferring heat (big pipe). That's why the transistors have metal tabs or metal cases bolted to metal heat sinks. The transfer from the heat sink to the air is much less efficient (little pipe)which is why the heat sink are so darned big (lots of little pipes-that's what the fins on the heat sink are for).

The one other factor that I haven't mentioned it that the greater the temperature difference on either side of the "->" the more heat flow you will get.

Sooooo....

Moving the air with a small fan is an easy way to get 20-30 degree more temperature difference which definitely helps. It really doesn't matter which way you blow the air as long as it's AWAY from your components. However heat still has to flow through those pipes and therefor the effect on junction temperature is going to be less than the 20-30 degree air temperature.

A rule of thumb is that for every 10 degrees C (junction temp) decrease you'll double the life of your power electronics. 10C is about 18F.

Now the real question is how long was the unit designed to last without forced air flow?

In answer to the next question, yes, work is a little slow at the moment.
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LG 65" OLED
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#98001 - 04/10/18 05:48 PM Re: 976 is warm [Re: kiwiaudio]
Deromax Offline
Gunslinger

Registered: 11/05/07
Posts: 61
Loc: Shawinigan, PQ, Canada
If the manufacturer thought their gear needed fan cooling, they would have installed some. You are over thinking all this heat thing, really!
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" I hear no highs, I feel no lows, it sounds like crap, it must be Bose "

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#98003 - 04/11/18 06:45 AM Re: 976 is warm [Re: Deromax]
Owl's_Warder Offline
Desperado

Registered: 06/29/01
Posts: 893
Loc: Grants Pass, OR
Originally Posted By Deromax
If the manufacturer thought their gear needed fan cooling, they would have installed some. You are over thinking all this heat thing, really!

Not really. Admittedly we're having fun taking the topic to a bit of an extreme. However, it IS an important topic to keep in mind. Manufacturers design their gear based on sufficient ambient cooling being available. Once equipment is placed within racks, cabinets, or other types of enclosures, sufficient ambient cooling is often NOT available and the air must be circulated somehow to compensate.


Edited by Owl's_Warder (04/11/18 06:46 AM)

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#98005 - 04/11/18 07:15 AM Re: 976 is warm [Re: kiwiaudio]
kiwiaudio Offline
Gunslinger

Registered: 01/16/11
Posts: 78
Good point Owls. Id like to think a manufacturer would be anticipating a worst case environment, but i believe they anticipate us upgrading tech gear way before it reaches it life expectancy. In my case, that holds true for everything but amplifiers. I also believe a max 10 year life is also designed into everything these days. Now that im almost 60, i can look back at so many things that have reached the 10 year plateau, then died. Washing machines, refrigerators, water heaters, ovens, garage door openers, furnaces, air conditioners etc. Low quality often means getting a week beyond the warranty before it pops !
Remember your grandmothers washing machine that seemingly lasted Her whole life! Not going to sell a whole lot of anything if it lasts forever, so how do i get Kiwi to buy 6 of everything during his lifespan ?


Edited by kiwiaudio (04/11/18 07:19 AM)
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Speakers are all built by myself utilizing Dynaudio Drivers
Second room: Yamaha receiver, Musical fidelity X10D tubes, Carver C9 holographic pro.

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#98006 - 04/11/18 08:12 AM Re: 976 is warm [Re: Owl's_Warder]
Deromax Offline
Gunslinger

Registered: 11/05/07
Posts: 61
Loc: Shawinigan, PQ, Canada
Originally Posted By Owl's_Warder
Once equipment is placed within racks, cabinets, or other types of enclosures, sufficient ambient cooling is often NOT available and the air must be circulated somehow to compensate.
IMHO, if the cabinet have rear vents at the bottom and the top, a natural draft will establish and should be enough even without fans, unless you are in tropical climate with no A/C! wink
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" I hear no highs, I feel no lows, it sounds like crap, it must be Bose "

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#98007 - 04/11/18 08:17 AM Re: 976 is warm [Re: kiwiaudio]
Deromax Offline
Gunslinger

Registered: 11/05/07
Posts: 61
Loc: Shawinigan, PQ, Canada
Originally Posted By kiwiaudio
I also believe a max 10 year life
There are exceptions! I have a few Bryston amps from the mid 80s that are powered 24/24 since I got them, still going strong. I once had a 2B-LP that got so much overheated in its previous life that the black anodized cooling fins had turned to purple!

But I disgress! smile


Edited by Deromax (04/11/18 08:18 AM)
_________________________
Eric Desrochers
http://www.blu-ray.com/community/gallery.php?member=Deromax

" I hear no highs, I feel no lows, it sounds like crap, it must be Bose "

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#98008 - 04/11/18 09:20 AM Re: 976 is warm [Re: Deromax]
Helson Offline
Gunslinger

Registered: 03/21/12
Posts: 208
Loc: USA
Originally Posted By Deromax
Originally Posted By Owl's_Warder
Once equipment is placed within racks, cabinets, or other types of enclosures, sufficient ambient cooling is often NOT available and the air must be circulated somehow to compensate.
IMHO, if the cabinet have rear vents at the bottom and the top, a natural draft will establish and should be enough even without fans, unless you are in tropical climate with no A/C! wink
You bring up the other factor to be mindful of with these devices. If you're in a humid climate, condensation will be a concern. That, and heat buildup are the two things to be mindful of, and both can be handled with a small fan. With condensation, keeping the air moving is the key. As the unit is cooling after powering off, the condensation forms. Then a corrosive process begins from the moisture that settles on the internal components.
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#98013 - 04/11/18 02:10 PM Re: 976 is warm [Re: kiwiaudio]
XenonMan Offline
Desperado

Registered: 04/08/08
Posts: 2560
Loc: Columbus,North Carolina
You would only get condensation if you cooled the unit below ambient air temperature. That is unlikely to happen unless you installed additional cooling equipment inside the gear. Moving ambient air past the components is not going to harm the equipment unless there is dirt in the air. I have a 1976 Yamaha CA-800 integrated amp that is still going strong and has never been in the shop.
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Music system
Model 990/7500/Magnepan 1.6 QRs/Technics SL1200 MK2/Aperion S-12 Subwoofer/OWA3/Sony NS75H DVD
APC H15 Power Conditioner

TV System
Large Advent Loudspeakers/ Polk center/Monoprice surrounds/Panasonic Viera 42 inch/Onkyo HT-RC260/Sony BDP S590/Directv


Home Theater System
Onkyo PR-SC886/Outlaw 7125 Klipsch RF-82 L/R,RC-62 center, RB-35 SR/SL, BENQ HT1075, Outlaw LFM1-EX/OPPO BDP-83/Directv
Harmony ONE
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#98230 - 11/27/18 09:20 AM Re: 976 is warm [Re: kiwiaudio]
975 destroyer Offline
Gunslinger

Registered: 09/07/15
Posts: 106
Loc: Georgia, US of A!
In light of this thread, minimum space above a 976 for adequate ventilation? Didn’t see anything specific in the manual.

Sidenote: I have some (still functional) gear from the early & mid eighties...

Thnx, Tony


Edited by 975 destroyer (11/27/18 09:20 AM)

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#98231 - 11/27/18 05:53 PM Re: 976 is warm [Re: kiwiaudio]
XenonMan Offline
Desperado

Registered: 04/08/08
Posts: 2560
Loc: Columbus,North Carolina
2 inches on each side and the top should be enough but if it is running too warm then add some forced ventilation.
_________________________
Music system
Model 990/7500/Magnepan 1.6 QRs/Technics SL1200 MK2/Aperion S-12 Subwoofer/OWA3/Sony NS75H DVD
APC H15 Power Conditioner

TV System
Large Advent Loudspeakers/ Polk center/Monoprice surrounds/Panasonic Viera 42 inch/Onkyo HT-RC260/Sony BDP S590/Directv


Home Theater System
Onkyo PR-SC886/Outlaw 7125 Klipsch RF-82 L/R,RC-62 center, RB-35 SR/SL, BENQ HT1075, Outlaw LFM1-EX/OPPO BDP-83/Directv
Harmony ONE
Blue Jeans and Monoprice interconnects
APC H15 Power Conditioner

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