Heat sinks for LM3875TF

monitoraudio · 7th March 2012, 02:25 PM

I am hoping for some advice and help

I have a pair of gainclone dual mono amplifiers, with a separate power pack

Each mono has its own case, approx 17 x 10 x 5 cm, of metal construction

I have noticed after extended use the case gets relatively warm

I was thinking of sound deadening each case, which could make heat dispersal worse (?)

Should I be thinking of fitting heat sinks to each LM3875TF ?

If so, how do I go about selecting a heat sink and is it just a case of selecting my desired heat sink and using the thermal adhesive tape supplied ?

Here is hoping for some help

lanchile · 7th March 2012, 03:50 PM

Can you post pictures?

monitoraudio · 7th March 2012, 03:52 PM

What specifically do you want to see pictures of ? General pictures of the amplifiers or of the circuit boards ?

lanchile · 7th March 2012, 03:59 PM

of where those IC's are mounted! are you using the chassis as a heat sink?
I build those amps long time ago from Audiosector and the IC's did not get hot at all, but again I used big heat sinks.

monitoraudio · 7th March 2012, 04:01 PM

They are mounted on a pcb, which is not in contact with the chassis, it has a fastening screw coming through the bottom of the casework which raises them approx 1cm from the bottom of the case

SoIL4x4 · 7th March 2012, 04:30 PM

So your saying the ic has no physical connection to anything in the enclosure aside from the pins into the pcbs.

monitoraudio · 7th March 2012, 04:37 PM

You are quite correct, no physical attachment to anything else in the enclosure, besides pins and pcb

lanchile · 7th March 2012, 04:38 PM

Quote:

Originally Posted by monitoraudio

They are mounted on a pcb, which is not in contact with the chassis, it has a fastening screw coming through the bottom of the casework which raises them approx 1cm from the bottom of the case

What?

are you saying those IC's are "floating" and nothing on the back to dissipate heat?. if this is right....YOU MUST PUT HEAT SINKS TO THE IC'S!!!!

monitoraudio · 7th March 2012, 04:54 PM

Hence my original post

What type of heat sink should I use and should I attach it directly to the chip ?

AndrewT · 7th March 2012, 04:56 PM

Look at the National datasheet for heatsink guidance.
Then I suggest you double their suggested sink size.

7th March 2012, 02:25 PM	#1
monitoraudio diyAudio Member Join Date: Nov 2010 Location: UK	Heat sinks for LM3875TF I am hoping for some advice and help I have a pair of gainclone dual mono amplifiers, with a separate power pack Each mono has its own case, approx 17 x 10 x 5 cm, of metal construction I have noticed after extended use the case gets relatively warm I was thinking of sound deadening each case, which could make heat dispersal worse (?) Should I be thinking of fitting heat sinks to each LM3875TF ? If so, how do I go about selecting a heat sink and is it just a case of selecting my desired heat sink and using the thermal adhesive tape supplied ? Here is hoping for some help

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7th March 2012, 03:50 PM	#2
lanchile diyAudio Member Join Date: Sep 2008	Can you post pictures?

7th March 2012, 03:52 PM	#3
monitoraudio diyAudio Member Join Date: Nov 2010 Location: UK	What specifically do you want to see pictures of ? General pictures of the amplifiers or of the circuit boards ?

7th March 2012, 03:59 PM	#4
lanchile diyAudio Member Join Date: Sep 2008	of where those IC's are mounted! are you using the chassis as a heat sink? I build those amps long time ago from Audiosector and the IC's did not get hot at all, but again I used big heat sinks.

7th March 2012, 04:01 PM	#5
monitoraudio diyAudio Member Join Date: Nov 2010 Location: UK	They are mounted on a pcb, which is not in contact with the chassis, it has a fastening screw coming through the bottom of the casework which raises them approx 1cm from the bottom of the case

7th March 2012, 04:30 PM	#6
SoIL4x4 diyAudio Member Join Date: Nov 2011 Location: Carterville, IL	So your saying the ic has no physical connection to anything in the enclosure aside from the pins into the pcbs.

7th March 2012, 04:37 PM	#7
monitoraudio diyAudio Member Join Date: Nov 2010 Location: UK	You are quite correct, no physical attachment to anything else in the enclosure, besides pins and pcb

7th March 2012, 04:54 PM	#9
monitoraudio diyAudio Member Join Date: Nov 2010 Location: UK	Hence my original post What type of heat sink should I use and should I attach it directly to the chip ?

7th March 2012, 04:56 PM	#10
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Look at the National datasheet for heatsink guidance. Then I suggest you double their suggested sink size.