Axiom Home Page Forums General Discussion Technical Questions Cooling Fan

i know a few of you guys have talked about external cooling fans to help in keeping your receivers from getting too hot. i have decided to get one as a precautionary measure, but i have a question about how to use it.

i will obviously place the fan on the top of the receiver, towards the rear where the little slits are in the metal.. but, would i want to place the fan blowing DOWN, to blow cool air into the unit..? or, would i want to place the fan blowing UP, so it will suck the hot air out of the unit..? do i make sense..?

any help or suggestions would be appreciated..

bigjohn

I think you want to suck instead of blow (age old question of which is worse comes to mind...).

I believe the units are designed to use convection to let the hot air rise out of the top vents; I'd think it better to reinforce or accelerate that design principle rather than turn it upside-down.

Does your receiver get hot?

I have a Denon 1804 with only about 2" of space on top/sides, inside a glass-front cabinet. Even after playing movies at loud volumes, it isn't anything beyond "warm". I mean, I applaud your conscientiousness, but I just don't have the outlets or time to wire something else up, and I'm concerned that the potential noise is going to irritate me beyond the benefit. I'm also concerned about forcibly drawing dust through the receiver; the fans on my computer get much nastier looking than my hi-fi gear ever does.

Hey John, what kind of fun are you getting? DC or AC? Or powered through USB port of some other device? My Rotel RB-1080 power amp gets really hot (though never has shut down) and I want to buy one myself.

I posted something similar on Club Rotel shown on This Link It has a lot of info, and I was really impressed with DIY work of PewterTA in that forum. You may wanna check that for ideas, however, I am not able to do any of those myself for now. I am looking for something simplier.

Easy. Just buy a cool running power amp and plug it into your preouts. Problem solved.

Oh yeah, never mind. The fan is a little cheaper. . .

thanks for the advice.. my first impression was to suck the air out, but i just wanted some back-up for my idea.

my Onkyo does get a little hot during high volumes on long movies, but it isnt horrible. and it is hot, not just warm. it is uncomfortable to put your hands on it for more than 5-7 seconds. it wont BURN you or anything, but it is definitely more towards hot than warm.. sorry, i am jabbering.. anyway, here is why i am thinking about getting the fan.

right now, because i have cable, and limiting inputs on my TV, i dont use the receiver for normal everyday TV watching. i just use the speakers on the TV, and only use the receiver for listening to cd's, or watching movies on DVD.. so at best, the receiver is only on for 2-4 hours at a time, maybe more on the weekends. but, i am fixing to get a satellite dish, and i will connect it thru the receiver, and then to the TV.. so, pretty much, whenever the TV is on, the receiver will be on. so, it will go from being used 2-4 hours a day.. to being used 6-8 hours a day, depending on how much TV is watched when i am at work. so, as just a safety measure, i would like to get the fan to combat any stress from heat that might occur.

i am just gonna plug it into the dedicated socket on the back of the unit.. so, when the unit is on, the fan is on.. unit off, fan off.. easy...

EDIT- thyname, DC all the way.. its just easier..there is a little mom & pops electrical shop here in town that already has the fans with plug-in cords attached for real cheap..

bigjohn

My only concern would be noise. I think with the $ you already have invested in the rest of your equipment, it may be wise to nab one of those 2 channel Onkyo amps to power the mains. $200, I think.

that makes two replies with concerns about the noise from the fan..? are the fans THAT loud..?

i might have to get one from that store, and bring it home and see just how loud it is.. they will let me do that before i buy.. gotta love hometown service..!!

bigjohn

Aha, see? I was serious after all. . .

My HK 7200 is a small heater in my room. Enough so that it is uncomfortable to watch movies in the summer. I've added an external power amp and it really does take the majority of the load off the receiver.

In reply to:

---

EDIT- thyname, DC all the way.. its just easier..there is a little mom & pops electrical shop here in town that already has the fans with plug-in cords attached for real cheap..

---

I don't have a DC power source though. Anybody any idea on where to find a DC cooling fan with its own DC power source/adapter?

Thanks a lot!!

dude, i had a brain fart man..

i meant AC, just a straight 110 plug, like going into the wall.

geez, i screwed the pooch on that one..

bigjohn

with it being a (relatively) small fan, it shouldn't be problem running it off of one of the outlets on the back of the reciever. a fan like that is a pretty small load so you shouldn't worry about tripping the reciever. and if you do have to get a DC fan, radio shack has adapters in a multitude of voltages, so that wouldn't be a problem.

p.s.- you know you love the funky wookie!!

I have my amp and DVD player plugged into the back of my Denon. No problems at all.

bigjohn
Some of the fans are loud. I initially had one from Rat Shack mounted on the back of my HT cabinet and plugged in to the back of the 2805. The hum of that thing drove me nuts. Took it off.
I have seen some on e-bay and other places that are made for cooling HT gear, and are supposed to run almost silent.

John, if Tom's suggestive language didn't get you yourself too hot and you're still reading this, I'd suggest not worrying about a "precautionary" measure if your receiver isn't glowing red-hot. Fans can be noisy.

thanks for the advice guys.. i reckon i will just wait til i get the satellite, and just see how hot it runs when being on for several hours at a time.. if its not too bad, then i will just scrap the whole idea..

although, i do like the idea of getting a dedicated amp just for the fronts.. a nice monoblock might be in order.?

bigjohn

2 "mono"blocks?

John, take a look at the link in my sig. I'm using an 8inch silent external fan from radio shack. $12 if I recall correctly. It keeps my receiver ice cold.

I have it blowing up to suck the air out as others have already stated. The fan is extremely silent if standing up by itself but does make a small humming sound when placed on top of receiver from sucking the air so fast throiugh the vents. Unless you are really anal about or are trying to listen for it, you will barely notice it after awhile.

I listen to my movies loud so I don't even hear it except for extremely quiet scenes. Again, it is a very faint sound. I had to splice an AC cord to it (since it is made for computers or electronics I believe) and plug it into the back of the receiver so it turns on with the receiver.

My HK avr630 runs hot with the M80's. Until I ever decide to run seperate amps for the fronts, I will be sticking with this option.

Hey Shag:

Is your fan DC or AC? If DC, where is it plugged, do you have your own DC power source?

thanks a lot!!

Nice thing about stuff from Radio Shack is they have the part numbers on them. I looked it up. Here's the link for the fan I have.

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=273-241

Like I said before, if standing upright by itself you can't even hear it. Lying down on top of the receiver it makes a humming noise because its sucking the air out so fast.

You'll have to decide for yourself if it bothers you. I did have to splice it with a plug, also from Radio Shack, and I plug it into the back on the receiver. Reciever on fan on, receiver off fan off.

I did much the same (Radio Shack cooling fan with Radio Shack DC power supply, using receiver plug). In my case, the receiver is inside an armoire wih 1" of clearance above it. With the door closed, the inside gets really so hot that I worry about damage to the CDs stored inside, plus the possibility of damage to the furniture itself. (The armoire is Ethan Allen and costs more than my sound system combined!) So I put a fan sucking air out of the armoire itself. But the air circulation is pretty lousy, and eventually I gave up and now just leave the door open and the fan off (the fan isn't absolutely quiet and I'm really picky about noise). The way I figure it, the receiver has lasted 3 years already without failing, and if it dies from overheating tomorrow I'll just go buy a better one. Electronics will die sooner when they run hot (many degradation mechanisms in ICs are accelerated rapidly by temperature, often something like a factor of 3X per 25deg C). But I'd rather enjoy the sound on a short-lived receiver than have noise for a very long time.

Interesting post Bigjohn. My onkyo runs hot as well. My old Onkyo that I had for just under 10 years ran hot as well. In fact the friend I sold it too has it in a small cabinet and had it melted the feet of his dvd player that was placed on top of it. (house cleaner closed the cabinet while listening to music and cleaning the house, the cabinet went thermonuclear).

I have considered the fan idea but worry that the noise would be pronounced although probably no more than my dvd player making noise while spinning the little discs. Definitely let us know how it goes if you install the fan.

I have run my newer 601 for hours and hours and it does get pretty scary hot but so did the old one and its still kicking after a decade of heat.

The only problem in my case was I NEEDED the fan. My HK630 was running hot enough to constantly kick in the automatic shutdown circuitry when the room was warm and depending on how load I was playing it. This is most likely because I am running the M80's.

So until I use separates for the M80's, I'll be sticking with the fan.

The way to keeping fans quiet it to run them lower than their specified voltage. I run 3 DC fans, all are 12Volt fans. I run them at 5 volts, they run plenty fast enough to move the air, and they are very quiet.

Heat greatly reduces the life of electronics, so even of your amp is not switching off, you may still want a fan, it's always better to run cool.

My Denon runs hotter than my monos. How do you limit fan speed on your fans?

Yeah, I'd like to know too. It would probably reduce the noise of my fan too even though its not much. Problem is the fan really runs faster than you need it to cool the receiver down. Slowing it to half speed would be ideal.

To slow the fan speed down, just reduce the input voltage. It won't harm the fan, if it's a DC fan. I use a power supply that has multpile outputs. 5V, 12V, 24V. You can get a power supply like this at Radio Hack, or partsexpress.com

If the fan is a 24V fan, run it at 12V, if it's a 12V fan run it at 5V.

Like This?

A variable power supply would definitely give you more control and with enough current allow you to run a chain of fans at lower than normal speeds. Ideally you would want the largest DC fan you can get and run it below its rated voltage. The larger fan running at a lowe speed will typically produce less noise than several smaller fans. More importantly is that you will have fewer fans on your equipment. As an example, you can look at Mouser Electronics (http://www.mouser.com/catalog/622/1316.pdf) where you would choose the largest fan with the lowest operating RPM.

It is true that heat breaks down semiconductors. Capacitors also do not like heat. I had to repair a friends NAD cd player that had burnt out semiconductors. The replaced parts also ran hot. That was about four years ago and the unit is still in operation.

A fan is a good idea. Period.

Thanks for the tip! I'm probably going to have to put in at least one fan behind the 525 once i get the doors on my entertainment center, any time in the next 20 years or so...

I guess I should also point out that fans do have an inlet effect. You do not want to put the fan directly over the unit unless you have a hole cut in your cover grill. The expression used in the HVAC industry is "The world doesn't suck, it blows". By this it means that fans operate more efficiently by blowing through a restriction rather than drawing through it. Fans need a bit of space at their inlet to operate most efficiently (and more quietly).

As another example, some computer cases draw and blow through the case for a more efficient cooling operation.

The best install would require further raising the unit to install a fan underneath, have it blow up through the unit (obviously to take advantage of natural convection).