F5 Turbo Circuit Boards - Page 111 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 21st March 2012, 10:58 PM   #1101
diyAudio Member
 
Join Date: Jan 2010
Location: Harrow, UK
Quote:
Originally Posted by labjr View Post
The idea is to remove heat from the output device. Spreading it over a wide area is the way to do it.

Because the output devices run so hot, it only makes sense that the heat flowing through a small area between the output device and the heatsink is more concentrated than anywhere else. Thus is it would seem that reducing the thermal resistance at that point would be most beneficial.
So let me get this straight in my head.

A heat spreader is designed to spread the heat from an output device over a wider area.
The only way that I can see a heatspreader doing that better than directly mounting onto a heatsink would be if the thermal efficiency of the heat spreader was much higher than the thermal efficiency of the heatsink.
e.g. If the heatspreader was made of say copper and the heatsink was say aluminium. In that case then I can understand why somebody would use this method.
That therefore begs the question; what material is the heatspreader made of, and; how efficient is the thermal transfer across the junction of the heatspreader and the heatsink.
  Reply With Quote
Old 21st March 2012, 11:01 PM   #1102
diyAudio Member
 
Join Date: Feb 2009
Quote:
Originally Posted by labjr View Post
The idea is to remove heat from the output device. Spreading it over a wide area is the way to do it.

Because the output devices run so hot, it only makes sense that the heat flowing through a small area between the output device and the heatsink is more concentrated than anywhere else. Thus is it would seem that reducing the thermal resistance at that point would be most beneficial.
and when the heatsink is not up for the job, let the spreader do it.
thats my point don't conentrate the heat on the sink. thats what you trying to avoide
a big spreader does the job better then multiple smal ones. (and heatsinks with thin base)
the smal one's will not spread the heat very much.
  Reply With Quote
Old 21st March 2012, 11:03 PM   #1103
diyAudio Member
 
Join Date: Feb 2009
Quote:
Originally Posted by UKToecutter View Post
So let me get this straight in my head.

A heat spreader is designed to spread the heat from an output device over a wider area.
The only way that I can see a heatspreader doing that better than directly mounting onto a heatsink would be if the thermal efficiency of the heat spreader was much higher than the thermal efficiency of the heatsink.
e.g. If the heatspreader was made of say copper and the heatsink was say aluminium. In that case then I can understand why somebody would use this method.
That therefore begs the question; what material is the heatspreader made of, and; how efficient is the thermal transfer across the junction of the heatspreader and the heatsink.
exactly
without any numbers or experiance to back it up. i think copper is the best way to go. you need a material that is softer then the heatsink.

Last edited by AudioSan; 21st March 2012 at 11:05 PM.
  Reply With Quote
Old 21st March 2012, 11:07 PM   #1104
diyAudio Member
 
Bksabath's Avatar
 
Join Date: Dec 2007
Quote:
Originally Posted by UKToecutter View Post
I guess the problem with a heat spreader is achieving good thermal coupling with the main heatsink.
How do you guys manage that?
Graphite grease machined surfaces and about 10 hours of han lapping
(one surface against the other in place) first with carbide and finish off with baking powder till is all shiny and mirror like and the 2 pieces stick togheter as if magnetised (No I did not invent magnetic cooper it has someting to do vith the vacum formed between the 2 )

2 heat sink 2 heat spreders each is 40 hours of rubbing the pieces togheter by hand.

Then clamp the lot with loads of bolts for wich sink has to be drilled and elicoils fitted

and Spreader got to be drilled cuntersunk and oversiszed holes to alowd for expansion.

If one is in to self punisment and or self medication is easily done but the use of Pillar drill is strictley forbiden
  Reply With Quote
Old 21st March 2012, 11:13 PM   #1105
diyAudio Member
 
Bksabath's Avatar
 
Join Date: Dec 2007
Quote:
Originally Posted by labjr View Post
I once thought of mounting the P type and N types devices on separate copper heat spreaders electrically isolated from the aluminum, so you can mount the outputs directly without any insulator reducing the case temperature even more.
I was thinking about this but same expert came up with the increased capacitance that the heath spreder wuld have in this case.

Rather than get in to the argument( I could not mathematicaly prove it wrong) I went for kerafoll onder the Mosfets.
  Reply With Quote
Old 21st March 2012, 11:16 PM   #1106
diyAudio Member
 
Join Date: Feb 2009
Quote:
Originally Posted by Bksabath View Post
Graphite grease machined surfaces and about 10 hours of han lapping
(one surface against the other in place) first with carbide and finish off with baking powder till is all shiny and mirror like and the 2 pieces stick togheter as if magnetised (No I did not invent magnetic cooper it has someting to do vith the vacum formed between the 2 )

2 heat sink 2 heat spreders each is 40 hours of rubbing the pieces togheter by hand.

Then clamp the lot with loads of bolts for wich sink has to be drilled and elicoils fitted

and Spreader got to be drilled cuntersunk and oversiszed holes to alowd for expansion.
hehe torture
If one is in to self punisment and or self medication is easily done but the use of Pillar drill is strictley forbiden
hehe torture
  Reply With Quote
Old 21st March 2012, 11:32 PM   #1107
diyAudio Member
 
Bksabath's Avatar
 
Join Date: Dec 2007
Okey dokey


Recap
Buy heat sink cost loads of dosh still base plate is only 10mm.
That conduct heat to fins that radiate heat to air.

Duble thikness of base plate it reduces the times the heat takes to get to the fins that radiate heat to air.

Heath travels 2 times as fast on cooper when compared to aluminium

Aluminium Radiate heat much better than cooper as cooper is like a mirror

Black radiate heat better than white

At least this is the symple explanation no need to complicate things.

Use Kerafoll 86/83 I do not know of better specs materiall

Kerafoll likes pressure duble the pressure reduces thermal impedence by half
There is a graph on data sheet and of the top of my head it show pressure up to 120 PSI for best performance but be carefull if you use proper screws with cuntersunk heads (IMO best advantagge with using heat spreaders) one may get to the point at whic the mosfect body crack with to much pressure.


Why I like to cuntersunk the screws heads on the heat spreaders?

Because the tread expecialy for M3 screws strips far to easy for my taste.

One has to use elicoil inserts to repair the tread or move the mosfets and drill new holes.

How many time did I change Mosfets on my boards / heat sinks?
Loads
how many new holes ?

Zero
  Reply With Quote
Old 21st March 2012, 11:43 PM   #1108
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
Quote:
Originally Posted by AudioSan View Post
demands 100% even surface on heatsink and heatspreader. witch is almost inpossible.
A surface grinder does 1 micron accuracy.

(me surface grinding press/extrusion die & mould parts at age 10)
__________________
The buck stops Here
  Reply With Quote
Old 21st March 2012, 11:51 PM   #1109
diyAudio Member
 
Join Date: Feb 2009
Quote:
Originally Posted by jacco vermeulen View Post
A surface grinder does 1 micron accuracy.

(me surface grinding press/extrusion die & mould parts at age 10)
machin grinding you dont get that by hand grinding.
so the cost will for most be high. and cheeper to buy heatsinks with 15mm straight base

Last edited by AudioSan; 21st March 2012 at 11:53 PM.
  Reply With Quote
Old 21st March 2012, 11:53 PM   #1110
labjr is offline labjr  United States
diyAudio Member
 
Join Date: Apr 2003
Location: MA
Here's an inexpensive soft-start module on ebay. Probably cheapo relays but maybe can be replaced with some better ones.

Class A power delay soft-start temperature protection board 110V/220V | eBay
  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
F5 clone boards (inc PSU boards) Tazzz Swap Meet 39 7th June 2014 07:02 AM
F5 Turbo is posted Nelson Pass Pass Labs 635 6th April 2014 10:51 AM
F5 turbo problems Rob Dingen Pass Labs 17 11th January 2013 08:38 PM
F5 Turbo ............. if only !!!!!! a.wayne Pass Labs 23 21st January 2012 02:24 AM
UGS Boards and F5 boards DUC985 Swap Meet 0 7th January 2009 07:21 PM


New To Site? Need Help?

All times are GMT. The time now is 03:52 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