Vertical positioning of transistor on heatsink

Eric · 3rd December 2002, 02:33 PM

Hi Everyone,

It seems that I'm the only one building a Pass Labs a40 around here, but hoping that some of you might have some insights to share with me.

The a40 has a total of 8 output transistors, for which I have purchased 8 Wakefield 423 heatsinks. The heatsinks are 5.5" tall and have three mounting positions: one near the top, one vertically centered on the heatsink, and one near the bottom of the sink.

My question is which location is best to place the transistor: in the middle, or in the bottom position? It seems that the middle position might get better heat distribution, but the bottom position might benefit most due to convection.

Does anyone have some insights to offer?

Thanks!
Eric

vpharris · 3rd December 2002, 02:48 PM

Probably in the middle. Actually it seems that they should be ideally mounted slightly offset toward the top. Look at the nice plot done by Wayne Sankey. You can use the software he used by getting it at the R-Theta website if you want to do the analysis.
http://www.passdiy.com/images/gallery/a2-p1-f3.gif

Eric · 4th December 2002, 03:14 PM

Thanks, Vince! I had forgotten about Wayne's thermal simulation. Looks like I'll be using the center mounting position...

Eric

3rd December 2002, 02:33 PM	#1
Eric diyAudio Member Join Date: Nov 2000 Location: Central PA, USA	Vertical positioning of transistor on heatsink Hi Everyone, It seems that I'm the only one building a Pass Labs a40 around here, but hoping that some of you might have some insights to share with me. The a40 has a total of 8 output transistors, for which I have purchased 8 Wakefield 423 heatsinks. The heatsinks are 5.5" tall and have three mounting positions: one near the top, one vertically centered on the heatsink, and one near the bottom of the sink. My question is which location is best to place the transistor: in the middle, or in the bottom position? It seems that the middle position might get better heat distribution, but the bottom position might benefit most due to convection. Does anyone have some insights to offer? Thanks! Eric

3rd December 2002, 02:48 PM	#2
vpharris diyAudio Member Join Date: Dec 2001 Location: Philadelphia	Probably in the middle. Actually it seems that they should be ideally mounted slightly offset toward the top. Look at the nice plot done by Wayne Sankey. You can use the software he used by getting it at the R-Theta website if you want to do the analysis. http://www.passdiy.com/images/gallery/a2-p1-f3.gif __________________ Vince Harris

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
tda2030a heatsink with transistor output	Goat	Chip Amps	3	31st January 2008 08:32 AM
Bi-Amp / Leach / Ops Transistor Heatsink Arrangement	ptah	Solid State	9	11th September 2007 03:17 PM
isolating power transistor from heatsink	Wagener	Solid State	10	23rd May 2004 09:57 PM
transistor placement on a heatsink	Mattyo5	Solid State	23	5th May 2003 09:25 AM
Help - Mounting transistor to heatsink	vsr123	Pass Labs	10	17th April 2003 11:43 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

4th December 2002, 03:14 PM	#3
Eric diyAudio Member Join Date: Nov 2000 Location: Central PA, USA	Thanks, Vince! I had forgotten about Wayne's thermal simulation. Looks like I'll be using the center mounting position... Eric

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)