Salas hotrodded blue DCB1 build - Page 224 - diyAudio
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Old 30th October 2012, 11:53 PM   #2231
Salas is offline Salas  Greece
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Nice to see a step by step photo report build. Keep us posted.
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Old 31st October 2012, 12:01 AM   #2232
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dimkasta, hard to guess how much the chassis will dissipate alone, but I think will be okay with the 10Rs. Good luck.
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Old 31st October 2012, 12:47 AM   #2233
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The other option that I really like is this

Click the image to open in full size.

The wood is wenge which I really like for that kind of work. It is heavy and dense which makes for an excellent vibration dissipation platform, and it is really beautiful as well.

The heatsinks are the ones used on the 4U HiFi 2000 dissipante series, and based on the F5 analogy they should be enough for tier 3 hotrodding..

The only issue with this approach is that the board's width is small, and in order to have the fets on the heatsinks the chasis will have to be narrow. The fets are also close together which means that they will have to be attached on the edge of the heatsinks, which might affect how the heat spreads to take advantage of the entire area of the metal. The narrow design also means less space to allow better isolation of the transformer and to keep the wires away from each other. It will require some careful design on how it should be layed out. Especially since I was planning to include a lightspeed in it.

Do you think those heatsinks would be enough to hold 2 fets each on tier 3 hotrodding? Perhaps it would be a solution to attach the board on the side on the heatsinks instead of on the wood.
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Last edited by dimkasta; 31st October 2012 at 12:53 AM.
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Old 31st October 2012, 01:10 AM   #2234
Salas is offline Salas  Greece
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What is the C/W for each of those?
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Old 31st October 2012, 08:15 AM   #2235
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Hi Tea-Bag,

any boards and kits left?

Regards,
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Old 31st October 2012, 08:34 AM   #2236
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Quote:
Originally Posted by Salas View Post
What is the C/W for each of those?
According to their site it is 0,31 C/W

So tier 3 would be 40W per rail or 80 watts total? Which means 0,31x80 = 24,8 above ambient temperature?

Which would mean roughly 50 degs celcius more or less if we consider the rating accurate and a mean ambient temp of 20-25 degs

Last edited by dimkasta; 31st October 2012 at 08:38 AM.
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Old 31st October 2012, 12:13 PM   #2237
Salas is offline Salas  Greece
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1A per rail is 20W per side for DCB1. Derate the sinks by 30% since Mosfets will be hot spots driving the metal surface, when any sinks are supposing full surface heating when characterized.
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Old 31st October 2012, 12:21 PM   #2238
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Quote:
Originally Posted by Salas View Post
1A per rail is 20W per side for DCB1. Derate the sinks by 30% since Mosfets will be hot spots driving the metal surface, when any sinks are supposing full surface heating when characterized.
Hmmm on this post you are specifying 40W per rail for 1R @12W
Salas hotrodded blue DCB1 build

Anyway, 20W per side means 10W per mosfet (and per heatsink).

30% derating on the heatsinks translates to 1deg Celsius per watt more or less, or 10 degs above ambient for 10Watts.

It should be really comfy? Or am I noobishly missing something?
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Old 31st October 2012, 01:16 PM   #2239
Salas is offline Salas  Greece
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Link says 2A 40W. It computes OK for my 1A 20W example.

30% would make them 0.31C/W (if honestly rated) circa 0.4C/W. Means just 8C above ambient for 20W on such a sink. IRFPs used are 0.83C/W RθJC. If you got 40C building up in enclosed box, each sink will be 48C. 1C/W thermal resistance silicone pads mount will give 58C on MOSFET cases. 10W each will give +8.3C to the chips inside. Below 70C or about if its a hot day or the box inside cooks more than assumed. Still cruising speed for 150C core melting point parts like these.
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Old 31st October 2012, 01:37 PM   #2240
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So is that scenario acceptable? 70C is still pretty hot

In any case, I think I will follow this scenario, raising the currents step by step checking how the heatsinks hold

Anyway, is the black board capable of handling such currents?

Last edited by dimkasta; 31st October 2012 at 01:45 PM.
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