Fan....Push or Pull?

[Deric]

Or should I say "Blow or Suck"?

I installed a fan in an amp that was blowing FETs in the VVR circuit....no more blown FETs...so far.

I've read conflicting info about whether it's better to push cool air in or pull hot air out of the cab.

Suggestions/comments appreciated!

[IMG:160:120]http://i40.photobucket.com/albums/e243/stumper1/TC15/th_TC15048.jpg[/img]
[IMG:160:120]http://i40.photobucket.com/albums/e243/stumper1/TC15/th_TC15047.jpg[/img]

[selloutrr]

PUSH the cold air in, the reason being, if you suck out the hot air it's not really cooling just venting.

[alanp]

Another reason for push is that if the area is dusty, and the fan is blowing out, air will be drawn in through the other gaps in the cab -- meaning dust will build up in all the other gaps, rather than being drawn through a fan that can be filtered if need be.

[Gaz]

PUSH the cold air in, the reason being, if you suck out the hot air it's not really cooling just venting.

I've never seen it this way. I thought the idea was to draw the heat out of the amp, just like the vents in the head cab - they're there to let heat out, not 'cold air' in.

[mika de silva]

alen p is on the money, drawing air in will create weird dust build ups.
In PC cooling, the idea is to create a positive pressure inside the case as to control the flow of air.
you blow the coolest available air over the parts of the amp that need cooling, simple.

gaz, the 'vents' in a head(and any amp really) rely on passive convection.
A fan gives us the ability to control the flow of air.

oh and as this is my first post.. hi!

[martin manning]

I think for the set-up as shown there will be a lot of recirculation, and probably more of it will occur when blowing in. I say this because the high-velocity exhaust from the fan will shoot straight across the chassis and hit the opposite wall. The warm air flowing out from the large rear vent will be at low velocity, and it can be easily entrained with the fan inlet stream. The power tubes and rectifier are on either side of the fan, so the air that is most likely to be recirculated is some of the hottest. A better cooling scheme would isolate the inlet from the exhaust to minimize this effect. Why don't you run a test? Place a thermometer probe next to the parts you are trying to cool and try it both ways.

[David Root]

The fan should blow as directly against the power tubes as possible, and still get all of them, which usually means angled somewhat for four tubes to get them all. See pic below of a Dumble Winterland, #3 for a typical arrgt.

[Bob-I]

PUSH the cold air in, the reason being, if you suck out the hot air it's not really cooling just venting.

Not accurate at all. Air must enter and exit from the amp to cool it, forcing air in or pulling out if there's no air flow will not help at all.

The key is to make sure you're pulling air from a source of cooling air. The direction of the fan depends on where the cool air is coming from. For example if the power tubes are in back pushing air into the back of the amp will only serve to heat up the rest of the amp, a fan in the back should pull the air out, but a fan in the front should push the air in. In either case there must be an opening in the front of the amp to allow air to the front and exit the back .

[selloutrr]

I double checked the direct. I powered on 3 SVT's if i put a piece of paper against the grill it sucks the paper and holds it. so the air flow is outside air - into the amp.

EDIT- Correct you need a way to get air in and out. but I assume the amp has a grill or open back it's not a 6 sided box with a single fan hole.

[Structo]

WHen I looked into this before what I came away with was, if you have the fan blowing on the power tubes, they will not be cooled evenly.
One or two of the tubes will receive more of the air current.

It's for this reason I think I would have the fan blowing out the back.
That way cool new air is sucked in through the grill cloth, which will act as a kind of filter, which may be a good or bad thing depending where the amp is located.

[JamesHealey]

You want to know about air cooling go speak to the guys on the formula one technical forum. They will know they're great with that kind of thing.

[Deric]

Hmmmm. On the amp pictured the grill on the back panel is the only ventilation - there is no grill cloth on the front, it's a solid panel. I intentionally placed the fan between the tubes to blow (or suck) air towards the part of the chassis where the FET is mounted.

Thanks for the input!

[Structo]

Either way Deric, you did a clean installation and I really like the bracket that you made for the fan.

What is the amp if I may ask?

Kind of weird that the front grill has no opening.

When I build the head cab for my 100w ODS, I plan on having very good ventilation with a large opening on the front.

[Deric]

Thanks Tom. The amp is a Trinity TC-15. I lent it to a buddy for a while and he managed to blow 2 FET's Not sure what happened as I've never had an issue and I'm pretty sure I play it a lot harder than he did. Regardless, I figured a fan couldn't hurt and I had a pile of old computer fans laying around... I had also added a cap before the VVR but it seemed to change the feel of the amp. Probably my imagination....but I took it out.

Right now I have the whole amp scaled and I'm starting to think the pre-amp just doesn;t sound good at lower voltages. Toying with the idea of just scaling the PI and PA....never done that before though. Not quite sure how to go about it.....

I bought the cab from Trinity also. Very nice cab but not much ventilation.

Found a new issue now... The PT hums a little. No worse than any other amp I have. Can't hear it at all....until I put it in the cab. As son as it's in the cab it's LOUD

[Structo]

My Heyboer PT in my D'lite hums a little bit. Not sure if it always did or if I just didn't notice it before.