lm4780 heatsinking...

morpheus82 · 27th July 2006, 04:14 PM

hi all!i have to place heatsink on my lm4780 and i have 2 questions...how many °/W do you use?and how do you bond the chip to the heatsink?by screws?

i don't want to crack it...

isn't there another way?like a piece of metal on the chip where placing screws?

morpheus82 · 27th July 2006, 04:15 PM

BTW, i planned to use pentiumII heatsink with double fan about 0.5°/W

ELiTeHaYDeN · 27th July 2006, 07:46 PM

yeah screws, nylon screws if u dont want the heatsink to be live, and a pad for insulation, other than that just metal screws and thermal compound, a pentium2 cpu heatsink and fan would probebly be ok, but it will run quite hot at full power, pick up a old pentium4/amd heatsink and fan, that will cool it fine without any fan modifications, use a couple of zenors to lower the voltage perhaps if its too loud(the fan).

i gotta test out my little p2p copy of nationals reference pcb, ill be using a p4 cpu heatsink and fan, so ill let you know how it goes.

click here for image

morpheus82 · 27th July 2006, 08:09 PM

WOW!!i've spent so much money for the pcb...

i never thought about this solution...

lgreen · 27th July 2006, 08:27 PM

Yes, a piece of metal works fine. Here is an example from Sparky the chipamp. Using a fan with this provides sufficient cooling. If you are very careful and carefully position some TO-3 insulating pads, and use nonconductive thermal grease, the sinks should stay isolated.

morpheus82 · 27th July 2006, 08:41 PM

thanx a lot, good idea but i think he uses screw and nuts but it's quite impossible to use nuts on pentium heatsink...

mike.m216 · 27th July 2006, 11:37 PM

the base on most computer heatsinks is thick enough to tap, and thread the bolts right into.

ELiTeHaYDeN · 28th July 2006, 03:24 AM

well i didnt end up using the p4 heatsink/fan, i found something else laying about that was easier to mount too.

should give u a idea, at even midly turned up volumes(no fan), it hits SPiKe(nationals protection setup) very quickly, a 120mm fan kept it at bay however, it was mildy warm.

the heatsink is finned at the back, about 3cm in height, but this particular heatsink has a very thin base, which appears to be a bad thing, it majorily hotspots.

Click here for image

morpheus82 · 28th July 2006, 06:57 AM

yeah, sure that heatsink won't have less than 2°/w at first glance, and i think it's really not enough...better to try with p4 if you want to use it avoiding spike action...

Niila · 20th February 2007, 01:23 PM

Didnt want to make new topic for my questions.

Parallel, not bridged.

Would that be enough for two parallel lm4780's? I listen music at normal/quiet volumes and use +-34V rails.

Another question btw, can i use two 120VA transformers for these chips..one for each?

Cheers!

27th July 2006, 04:14 PM	#1
morpheus82 diyAudio Member Join Date: Oct 2004	lm4780 heatsinking... hi all!i have to place heatsink on my lm4780 and i have 2 questions...how many °/W do you use?and how do you bond the chip to the heatsink?by screws? i don't want to crack it...isn't there another way?like a piece of metal on the chip where placing screws?

27th July 2006, 07:46 PM	#3
ELiTeHaYDeN diyAudio Member Join Date: Aug 2004 Location: Blenheim - New Zealand	yeah screws, nylon screws if u dont want the heatsink to be live, and a pad for insulation, other than that just metal screws and thermal compound, a pentium2 cpu heatsink and fan would probebly be ok, but it will run quite hot at full power, pick up a old pentium4/amd heatsink and fan, that will cool it fine without any fan modifications, use a couple of zenors to lower the voltage perhaps if its too loud(the fan). i gotta test out my little p2p copy of nationals reference pcb, ill be using a p4 cpu heatsink and fan, so ill let you know how it goes. click here for image __________________ mMmMmmMmmk?

27th July 2006, 08:27 PM	#5
lgreen diyAudio Member Join Date: May 2003 Location: San Diego, USA	Yes, a piece of metal works fine. Here is an example from Sparky the chipamp. Using a fan with this provides sufficient cooling. If you are very careful and carefully position some TO-3 insulating pads, and use nonconductive thermal grease, the sinks should stay isolated. __________________ Retired from DIY (2010) but still lurking now and again. My DIY audio projects- PartTimeProjects.com.

28th July 2006, 03:24 AM	#8
ELiTeHaYDeN diyAudio Member Join Date: Aug 2004 Location: Blenheim - New Zealand	well i didnt end up using the p4 heatsink/fan, i found something else laying about that was easier to mount too. should give u a idea, at even midly turned up volumes(no fan), it hits SPiKe(nationals protection setup) very quickly, a 120mm fan kept it at bay however, it was mildy warm. the heatsink is finned at the back, about 3cm in height, but this particular heatsink has a very thin base, which appears to be a bad thing, it majorily hotspots. Click here for image __________________ mMmMmmMmmk?

20th February 2007, 01:23 PM	#10
Niila diyAudio Member Join Date: Aug 2004 Location: Oulu	Another question Didnt want to make new topic for my questions. Parallel, not bridged. Would that be enough for two parallel lm4780's? I listen music at normal/quiet volumes and use +-34V rails. Another question btw, can i use two 120VA transformers for these chips..one for each? Cheers!


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27th July 2006, 04:15 PM	#2
morpheus82 diyAudio Member Join Date: Oct 2004	BTW, i planned to use pentiumII heatsink with double fan about 0.5°/W

27th July 2006, 08:09 PM	#4
morpheus82 diyAudio Member Join Date: Oct 2004	WOW!!i've spent so much money for the pcb... i never thought about this solution...

27th July 2006, 08:41 PM	#6
morpheus82 diyAudio Member Join Date: Oct 2004	thanx a lot, good idea but i think he uses screw and nuts but it's quite impossible to use nuts on pentium heatsink...

27th July 2006, 11:37 PM	#7
mike.m216 diyAudio Member Join Date: Jun 2006	the base on most computer heatsinks is thick enough to tap, and thread the bolts right into.

28th July 2006, 06:57 AM	#9
morpheus82 diyAudio Member Join Date: Oct 2004	yeah, sure that heatsink won't have less than 2°/w at first glance, and i think it's really not enough...better to try with p4 if you want to use it avoiding spike action...

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