Heatsink mounting issue - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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
Reply
 
Thread Tools Search this Thread
Old 2nd April 2001, 11:23 AM   #1
diyAudio Member
 
Join Date: Apr 2001
Location: Athens, Greece
I'm currently in the process of building a Pass Aleph 1.2. This is my third major DIY project after the A75 and Balanced Zen Line Stage both of which have served me right for the past two years. Especially the BZLS since it is completely remote controlled and constructed with audiophile materials. Needless to say they both sound wondefully. The temptation of the Aleph 1.2 is too much and despite the fact that i'm currently in no real need for heating equipment (the temp last week here in greece was 28 C) I HAVE to built it. I just finished shopping for the heatsinks and found some very nice pieces of sinks 30 cm x 19 cm with 6 cm fins. I'm usind 8 pieces for each channels (2 pieces in each side of the "cube") that I think should do the work. The sinks are rated at 0.4 C/W for a 15cm piece but I don't have much confidence in that rating (the supplier is a small manufacturing house that is manufactutring sinks for the local Telecommunications Industry) so I choose to have a surplus of I think 40% in my use of the sinks. I 've already drilled the sinks to make the joints needed for the chassis and the next step is to choose the mounting points for the transistor (IRFP 240). The dilemma I'm facing is whether to mount them tightly together (say 2cm distance between them) of spread them evenly across the entire available dimension (30cm). The second option would mean a distance between them about 6cm (and the same from the edges of the sinks). Both measurements reffer to three transistors in each sinks mounted vertically. As I see it in the first case the transistors will have a more uniform temperature (I'm puzzled though about what is going to happen to the middle on being surrounded by all that heat from both sides). In the second case I think the sink will be used more efficiently since the heat sources will be evenly spead along it's area (I'm worried though about what will be the temprature differential between the devices). I also know (or I think I know) that heat travells upwards. Will that mean that the sink will be slightly warmer on the upper side. That means that I have to mount the devices vertically slighty towards the bottom end? or mount them horizontally and risk wasting the sink? (I' donts think that by mounting horizontal along the 19cm dimension I will be able to make the sink work at it's edges). I' ve never worked with such a large sink, the A75 uses the tube like sink with a blower, and I don't know what to expect. I think though that sinks that big cannot disipate the heat quick enough if the heat source is concentrated somewhere on their centre and you end up using a portion of the sink. On the other hand the IRF Hexfets are, as I've seen with the A75, very sensitive to thermal differences and tend to loose their matching if they donot operate a the same teperature.
Any help ould be greately appreciated.
Thanks
__________________
Nikitas
  Reply With Quote
Old 2nd April 2001, 12:55 PM   #2
diyAudio Member
 
Join Date: Jan 2001
Location: Scandinavia
http://www.rtheta.com do such simulations on their heatsinks, and I think it is on-line.

One such simulation that was done for me was on one of their most radical heatsinks which had a 1cm base and a point insertion of heat. The heatsink was about 550mm long and about 25cm high and the heat distributed quite well even though the fabricated fins vere extremely long, tight-spaced, cerrated and "curled" (reads efficient).

So, I suppose you should look at the thickness of the base plate. An alternative is to place a bar on the heatsinks with the aim of distributing heat.

Petter
  Reply With Quote
Old 3rd April 2001, 09:15 PM   #3
diyAudio Member
 
Lisandro_P's Avatar
 
Join Date: Oct 2000
Location: Argentina
Send a message via ICQ to Lisandro_P
I once saw a large heatsing holding 5 power transformers with a large and thin cooper bar on it's back to help distribiting the heat more efficiently. It happens that aluminium is NOT a great heat conducer (atleast when compared with other metals), but, it can be anodized very easily, so it's todays standart for heatsink building. Perhaps the copper bar idea could help.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
heatsink mounting Q woodturner-fran Pass Labs 6 15th April 2008 09:00 PM
Mounting a Heatsink Bigman Chip Amps 8 13th December 2007 02:00 PM
mounting of outputs to heatsink bigpanda Solid State 10 27th April 2006 10:44 AM
Help - Mounting transistor to heatsink vsr123 Pass Labs 10 17th April 2003 11:43 AM
Heatsink mounting. JoeBob Solid State 3 21st January 2002 02:51 AM


New To Site? Need Help?

All times are GMT. The time now is 03:27 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2