| Raj1 |
Hi,
can any one please tell me if using multiple heatsinks on a chassis is effective when;
1) I have a 2 mono amps, each has two mosfets on it which obviously need heatsinks.
2) the outside of my chassis has approx enough room for 3 heatsinks per pcb.
3) as there are only 2 mosfets per pcb, this means that 2 of the heatsinks will each have a mosfet, whilst the third heatsink is partially 'redundant'..
4) all 3 of the heatsinks per pcbs will be on the same plate of aluminium,
how effeftive will the third 'redundant' heatsink, with no mosfet attached directly to it be?
arrrrgh! someone please reply!!!!!!!
Thanks
Raj |
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| joensd |
| quote: | | arrrrgh! someone please reply!!!!!!! |
I think youīd have to provide a little bit more information to get an answer to this.
What class is your amplifier for example?(A/AB/B...)
Whatīs the maximum output power?
Which mosfet packages are you using?
How thick is the aluminium plate and thermal rating of heatsinks?
Will you use insulators?
And still itīs not easy to calculate the final thermal resistance of this big heatsink.
Itīs nice to know all of this and especially the maximum power dissipation of the amp but some even experienced people would still say:| quote: | | We donīt calculate heatsinks. We just make them big. |
So....
Jens |
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| Mark A. Gulbrandsen |
"We donīt calculate heatsinks. We just make them big."
I love this line and I followed it to the hilt when I planned out my Aleph 2's. Here is a photo of my fairly cool running Alsph 2's...probably almost double what everyone else here is doing for heatinking....The pcb is 4"X6" for a size refrence. Each amp weighs in at almost 70 lbs!!
Mark |
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| Raj1 |
Hi,
the amp is a mosfet 250watt amp. At the moment I using a single 0.42k heatsink per pcb. The amp is being run at 250ma quiescient current, according to the designer the mosfets are dissapating around 35watts of heat at this setting. This only gives about 1 watt of class A op.
The new heatsinks I've seen are available from dick smith electronics in australia part no H3408 the thermal resistance is reputed to be 0.37oC/w
I was planning of placing three of these per side with only two of them connected to the heat sinks. However the mounting of the mosfets won't be central. Also I was thinking of using part of my old heatsinks over the front of the heatsinks. The gap between the two mosfets is around 40-60mm (can't quite remember) The space I have available is 300mm length by 200mm height. Is using a single large heatsink on the outside of the chassis preferable to using three like the ones mentioned Any ideas or other sugestions for heatsinks which are suitable?
Thanks
Raj |
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| joensd |
| quote: | | The space I have available is 300mm length by 200mm height |
For my next project (ZenV4) I want to use heatsinks with exactly that size.
Itīs the SK157 in 200mm height.
Itīs produced by Fischer Elektronik.
At this size you get 0,22K/W.(and thatīs only for the black anodized version which must be vertically orientated as well)
I only got an old catalog but at that time the heatsink was 65 and 76 for the black anodized one.
Jens |
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| Mark A. Gulbrandsen |
Ahhhh, So Dick Smith has finally landed his Hellichopper??? They used to have several stores here in the western states too but I think they packed up and flew back down under......don't know why though.
Mark |
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| Raj1 |
Hi Arne K,
What's the thermal rating for those babies?
Thanks
Raj |
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| Cobra2 |
If I knew, I would probably have emptied their stock...? :confused:
Arne K |
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| Raj1 |
| Well it's gotta be less than 0.2oC, what do ya reckon? |
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| Dennis Hui |
They appear to be very similar to:
http://www.aavidthermalloy.com/bin/...1=Change+Length
I'm using two in my mini-a amps under construction. Each
is dissipating around 30W and is pleasantly warm to
the touch but not hot. :)
I'll run the amps for a couple hours tonight and see if
I can get some meaningingful temperature info.
Cheers,
Dennis |
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| SkinnyBoy |
Do you guys like dicksmiths?? I find them sometimes cheaper, sometimes more expensive. I was going to use those heatsinks for my next (first) amp Raj1.... They were going to form the sides of the case, with either a clear plexiglass, or aluminium top and bottom.. :)
perhaps you could use more than 1 mosfet per heatsink (parallel), or still use 1 per sink, but use more heatsinks.. :) or did I miss something, (again) |
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| hifiZen |
Cobra2:
I bought four of those heatsinks from MECI. They were a better deal when they were listed at $5 each, but even at $10,they're a decent deal. I only used them for the Aleph-X prototype though, and I think I wouldn't use them for a finished amp. The ones I received were not anodized, and due to the lack of a single large flat surface on the back, it would be difficult to mount lots of transistors on there. Fortunately, they worked out just about perfectly for the Aleph-X rev1.0 boards, and the transistors mount just perfectly on there. I can't post the pic now, but when I get home in mid Jan, I'll post a few photos of the prototype, probably to the Aleph-X thread. |
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| Mark A. Gulbrandsen |
I got a great belly laugh out of this line tag........
Mark
Don't ask a question... halojoy might know an answer...
"BE LIKE HALOJOY, BE LIKE HALOJOY!!!" |
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| Dennis Hui |
Just a note that I agree with what Chad has said
about these heatsinks. Mounting banks of
devices on them will be a bit tricky. For something like
mini-a's (2 devices per channel), they're pretty
good.
FIY, I ran the mini-a's for two hours and measured
a rise of 21C @ 30W dissipation.
Cheers,
Dennis |
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