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Author Topic: WHERE IS HEAT GOING?  (Read 1727 times)
K7NSW
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Posts: 59




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« on: March 14, 2011, 07:12:07 AM »

Been surfing the e.ham SHACK SHOWCASE & SPOTLIGHT pages seeing how you guys arrange your stations.  Due to the nature of the equipment we use it looks like we all stack stuff up to some degree or another.  But I see more than just a few pictures showing hf amplifiers (usually tube types) jammed up close against wooden shelving on one side with other stuff pushed up against them on the other side plus more stuff piled up on top of them.  How is cool air getting into them?  I assume the hot exhaust air is going out the back?  Many photos show very little distance between the back of the amp and the wall behind it.  Gotta wonder about tube life in those buried amps.  Seems like I recall a "rule of thumb" suggesting/requiring 3 to 6 inches of unobstructed air space around and above an amp plus nothing restricting air flow around the base of the amp case.  Is that still good advice?  Or am I missing something?
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W8JX
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Posts: 6691




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« Reply #1 on: March 14, 2011, 07:42:37 AM »

Interesting observation. I do not think you need 6 inches around air intake source but you do need a open area to dump exhaust heat into. I have my amp a few feet away on a shelve away from radio to limit noise from its cooling fans and for better airflow around it.
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You can embrace new computer/tablet technology and change with it or cling to old fall far behind....
K7ZRZ
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Posts: 279




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« Reply #2 on: March 14, 2011, 10:52:27 AM »

K7NSW (Name?),

Some times we gotta do what we gotta do...  which you will see where I'm coming from if you look at my station picture on http://www.qrz.com/db/k7zrz. At times I have a Clippertion L amp down there on the bottom. I have never had a problem with heat, but then I don't do contesting or long winded transmitting of any kind.  Everyone's situation is different, but everyone should consider the points that you bring up and do the best they can to provide enough ventilation.

p.s. My station is in my Motorhome.
« Last Edit: March 14, 2011, 11:00:44 AM by K7ZRZ » Logged

Brian K7ZRZ
W5DQ
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Posts: 1209


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« Reply #3 on: March 14, 2011, 01:40:25 PM »

Another example of doing what you can in the space allowed is my setup with my AL-811. While the 811 isn't no legal limit amp, it still will spit out some respectable heat when pushed hard. The air intake is at the rear right hand side (looking from front). This just so happens to be at the far right edge of my desk so the intake air is not pre-heated from any other heat sources. The output is through a slotted grid at the left hand side of the amp which just happens to blow across the back of my PC monitor. To alleviate a possible heat build up in the area behind the monitor, I added a 120mm (~4") muffin fan mounted with stick-on 3/8" thick rubber feet that sits just below the amp output grid, parallel to the desk and blows air upward right after the hot air exhausts from the amp. This way the majority of the hot air is mixed with cooler air and the composite stream is diverted upwards into the upper part of the room. So far it seems to work good as the monitor never gets any warmer than the normal temp w/o the amp being used. The amp is placed at the only spot available for it on my desk and have it fit correctly so the fan arrangement is a necessary work around. Someday when I graduate to a big boy amp I'll probably have to re-layout the desk completely to get everything to fit and not overheat.
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Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
W8JX
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« Reply #4 on: March 14, 2011, 05:01:41 PM »

You know when they design a amp you would think they would have exhaust either going up or out back rather than sides. Some amps like my Dentron blow air out back.
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W5DQ
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« Reply #5 on: March 16, 2011, 08:59:03 AM »

You know when they design a amp you would think they would have exhaust either going up or out back rather than sides. Some amps like my Dentron blow air out back.

Exactly. I like the Alpha design of air in the back and exhaust straight up out the chimney. Having intake and output both at back requires careful placement not to set up a looping of air wher ethe amp draws in preheated air to 'cool' the amp. Sounds like a good start to thermal runaway Shocked

Gene
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Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
AA4HA
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Posts: 1646




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« Reply #6 on: March 16, 2011, 07:03:15 PM »

I run a Harris RF-7223 (3cx800a7 tube) that is mounted in a tall rack. The rack is a 23" wide ETSI standard so there is plenty of space on each side of the amp. The amp is in the topmost bay and has two dedicated cooling fans to just blow additional air into the side vents of the amplifier. (the amp normally sucks air in through a filter on the front and vents it out the back).

Heat is a killer, on all devices, on all components. The more air you can force into any electronic device the longer it will last.

I too wonder about some of the amps that are built into a custom cabinet with no side ventilation. Many have an air inlet on the bottom back part of the cabinet and an air discharge on the top back. It would be interesting to use an infrared temperature sensor to see exactly how much cooling is really going on to the parts that really matter.

Tisha Hayes
AA4HA
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
RUSS324
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Posts: 29




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« Reply #7 on: March 24, 2011, 04:06:16 PM »

I keep my AL-1500 off to my left. Easy access to tune and it sits on a table with nothing above or close to it. When I contest that bugger can pump out some heat. With my setup neither I nor my other equipment gets any of the heat. I have asked myself this same question. I also run an 811H and a SB-1000. Again I have them set up so that they have plenty of free air flow. Russ K8QF.
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K6AER
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Posts: 3535




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« Reply #8 on: March 28, 2011, 01:24:20 PM »

A lot of amplifiers bring the air in via the rear and exaust it out the top rear. This worls well. Cermamic tube amplifier have a more positive flow than glass  tube amplifiers.
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