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Post subject: Installing a fan
Posted: Tue Jan 17, 2017 12:29 pm
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I'm considering installing a 12Vdc brushless (PC) fan in the inside corner of my '68 single Showman head to blow across the tubes. But before I even go down this path I thought I'd ask to see if this is even advisable? Is there a preferred recommended way to do this? Or don't do it at all? If done right will noise be a problem?
It'd be nice if it was powered from the amp itself somehow, either the AC receptacle in the back or some other hardwired method. Otherwise I'd have to pack up a second extension cord and use a AC/DC wall adapter which is fine I suppose.

All the tubes are original except the 6L6's so I'd like to keep things as happy and healthy as possible for as long as I can.
This would obviously be a non-invasive install. No screws, drills, holes etc. 2-sided tape, Velcro and/or zip-ties only.


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Post subject: Re: Installing a fan
Posted: Tue Jan 17, 2017 1:01 pm
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I've owned and played Showmans for years and never felt the need for any artificial convection cooling (and neither did Leo). A fan is a waste of time IMO.

Arjay

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Post subject: Re: Installing a fan
Posted: Tue Jan 17, 2017 4:07 pm
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Retroverbial wrote:
I've owned and played Showmans for years and never felt the need for any artificial convection cooling (and neither did Leo). A fan is a waste of time IMO.

Arjay


Fair enough. Just sometimes when playing for long times at loud volumes it gets really hot. As in even the standby switch is hot to the touch.


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Post subject: Re: Installing a fan
Posted: Tue Jan 17, 2017 4:15 pm
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Of course it gets hot!

It's a tube amp drawing 260 watts of electricity.

Trust me......the heat is perfectly normal.

Arjay

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Post subject: Re: Installing a fan
Posted: Tue Jan 17, 2017 4:28 pm
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The amp last 48 years with no fan, why now ? Waste of time.


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Post subject: Re: Installing a fan
Posted: Wed Jan 18, 2017 6:37 am
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What I do sometimes with hot running guitar & hi-fi amps (esp those Class "A" type) --- is to put a portable room fan, on low speed facing up to ceiling. Just to disperse the heat. Vornado make some nice fans.

https://www.amazon.com/Vornado-Compact- ... rnado+fans


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Post subject: Re: Installing a fan
Posted: Wed Jan 18, 2017 7:24 am
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Fans can create noise - even brushless motors aren't EM silent. If adding one, I'd make sure it was electrically isolated with no common ground.
And you have to be careful how they blow too - you do not want to cool one side of a hot glass vacuum tube more than the other side.

If I had to cool an amp, I'd sandwich a peltier (TEC) between two heatsinks, with the hot side being on the outside of the amp, and the cold side being higher up than what needs to be cooled.


Last edited by arth1 on Wed Jan 18, 2017 12:22 pm, edited 1 time in total.

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Post subject: Re: Installing a fan
Posted: Wed Jan 18, 2017 7:34 am
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Really, the chassis and sockets of the amp should be designed to take heat, over time. Slow, steady movement of air UP & AWAY from the amp and tubes, is all I'd recommend for any tube amp. Usually, room convection flow is good enough.


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Post subject: Re: Installing a fan
Posted: Fri Jan 20, 2017 10:59 pm
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Don't do it, ever. There is simply no reason to put a fan anywhere near a tube amp... unless you just have to pull excess dust into the amp and shorten the life of it. :roll:

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Post subject: Re: Installing a fan
Posted: Sun Jan 22, 2017 3:03 am
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shimmilou wrote:
... unless you just have to pull excess dust into the amp and shorten the life of it. :roll:


+1000

Just to clarify: I worked on high-powered radar/radio/microwave equipment during the course of a 22-year military career. Virtually all of it was fan-cooled. However (and this is an important caveat) all of these fans drew their outside air through filters intended to remove particulates and ambient atmospheric impurities in order to prevent corrosion, oxidation, and dust from contaminating critical components within the equipment. Cleaning and/or replacing these filter elements was an integral part of the routine maintenance and servicing that this gear required for proper performance. Excluding commercial broadcast stuff, most fan-cooled audio equipment does not provide this protection.

Arjay

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Post subject: Re: Installing a fan
Posted: Sun Jan 22, 2017 5:28 am
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Good point about the filters. And all of the fans I've seen installed on guitar and hi-fi amps (tube or solid state) have the fan pointed in a direction for the hot air to be drawn out of the unit. Not blow cool air onto the components.


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Post subject: Re: Installing a fan
Posted: Sun Jan 22, 2017 9:09 am
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There are issues to pulling hot air through a fan. I have melted a few plastic fans down. It didn't seem that hot, but the rotating forces distorted the blades and left little balls of plastic trailing off the blades. The moral of the story is to use metal blades.
Filters also can cause problems with small fans pulling air through them. If there is any vacuum drawn between the fan and the filter, the motor speeds up. This causes the windings to overheat in short order and burn out the motor. I know it sounds simple, but design carefully.
This problem occurs in vacuum cleaners using cheap bags and furnace motors when you put in the expensive HEPA filters.
Dust accumulation is common in modern 2 channel rack mount amps. There is seldom any provision or recommendation for service intervals. Plugged filters and fan blades with impacted dirt cause excessive noise.

Speaking of plugged filters, I'm finding these small efficient space heaters I'm using this winter also suffer with dust accumulation.
The old heaters with coil elements would burn off most of the dust, but with these new ones, it accumulates and plugs up the element and the fan cage. I find I have to blow them out twice a year to maintain good efficiency..


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Post subject: Re: Installing a fan
Posted: Sun Jan 22, 2017 9:44 am
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I haven't seen melted fans. But, have seen non-functional fans on some amps. Ones that use or have added cheap Chinese made muffin-type fans. Good quality computer power supply types with ball bearings seem to work fine, for the long run.

But like already stated, the chassis gauge and quality of sockets --- as well as proper layout --- is usually good enough for most stand alone combo amps. :)


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Post subject: Re: Installing a fan
Posted: Sun Jan 22, 2017 10:19 am
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TimsAudio wrote:
The old heaters with coil elements would burn off most of the dust...


Those "old heaters" also caught fire frequently because of that, often with disastrous results.

Arjay

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