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 29th September 2007, 08:49 PM   #1
aldovan is offline aldovan  Brazil
diyAudio Member
 
Join Date: Jul 2005
Location: Curitiba
Default Heatsink, with MICA or NO ???

Dear friends

I am making a amplifier and I have a doubt.
Is best use a Mica between the power transistor and the heatsink, or is best the direct contact between the transistor and heatsink ? I am speak in hot dissipation .
My transistor do not need colector isolation.

Thanks,

Aldovan
  Reply With Quote
Old 29th September 2007, 09:59 PM   #2
diyAudio Member
 
Nico Ras's Avatar
 
Join Date: Nov 2005
Location: East Coast of South Africa
If you do not need isolation then do not use mica washers.
  Reply With Quote
Old 30th September 2007, 03:10 AM   #3
gni is offline gni  United States
diyAudio Member
 
gni's Avatar
 
Join Date: Sep 2006
The heatsink will be at the potential of the collector of the transistor
if the collector is the back of the transistor (which is most power
transistors).

That could be a bunch of -Ve or +Ve. But the possibility of better
heat transfer and no concern of breaking mica insulator.

NPNs and PNP cannot share the same heatsink; if bias transistor
and drivers are mounted on heatsink. . .they need to be
isolated with an insulator unless they have the same collector voltage.
The bias transistor will only respond to the NPN or PNP, but not both.

The heatsinks will need to be isolated from the enclosure.

That's all I know. . . there are some other good people here that could
straighten this out better. . . AndrewT and anatech come to mind. . .
they have saved my life several times.

Both my Yamaha M-45s and Rotel RB850 use silicon rubber. Pluses
and minuses to mica vs silicon rubber. . . can't hardly crack a silicon
rubber washer; mica washers are delicate but transfer heat better
I think.
  Reply With Quote
Old 30th September 2007, 07:51 AM   #4
MaxS is offline MaxS  France
diyAudio Member
 
Join Date: Mar 2006
Location: France
Hi,

Search for " Mica and goop " thread in Pass Labs directory.
__________________
Ca marche pas ! Tu ne l' as pas branché non plus ....
  Reply With Quote
Old 30th September 2007, 01:52 PM   #5
gni is offline gni  United States
diyAudio Member
 
gni's Avatar
 
Join Date: Sep 2006
Perfect discussion there. Covers all the topics. . . and ongoing.
  Reply With Quote
Old 30th September 2007, 10:31 PM   #6
aldovan is offline aldovan  Brazil
diyAudio Member
 
Join Date: Jul 2005
Location: Curitiba
Default I prefer no contact

Friends

In my case, I am building a class A hybrid anplifier.
I have one type of transistor( only NPN) in the heatsink.
I have a isolation between the heatsink and the chassis ground.
For me, the direct contact in the heatsink is best for transfer the hot. A termic paste is good for best results, too.

Thanks for the replays.

Aldovan
  Reply With Quote
Old 1st October 2007, 04:21 PM   #7
gni is offline gni  United States
diyAudio Member
 
gni's Avatar
 
Join Date: Sep 2006
Very good. . . .
  Reply With Quote
Old 1st October 2007, 04:32 PM   #8
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Default Re: I prefer no contact

Quote:
Originally posted by aldovan
In my case, I am building a class A hybrid anplifier.
I have one type of transistor( only NPN) in the heatsink.
I have a isolation between the heatsink and the chassis ground.
For me, the direct contact in the heatsink is best for transfer the hot. A termic paste is good for best results, too.
This must be a single ended. Are all the collectors fed from the same voltage potential? The sink could be the power supply rail.
The current sink cannot be more active devices on this same heatsink. Is the current sink a resistor?

Don't drop a metallic tool in there with a live sink.
__________________
regards Andrew T.
  Reply With Quote
Old 1st October 2007, 06:21 PM   #9
pooge is offline pooge  United States
diyAudio Member
 
Join Date: May 2003
Location: Northern Va.
You don't say whether or not the heatsink is isolated from body contact, or whether you are using a fan. If you are electrically isolating it from the chassis, not necessarily a good thing, it should be inside of the enclosure so it can't be touched. In that case, the air circulation around the heat sink may be more detrimental than an external heat sink with mica insulators.
  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
mica insulators aarifah Everything Else 0 20th August 2008 07:26 PM
Mica in Heatsink TO3 power transistor or no ? aldovan Solid State 2 6th June 2008 03:39 AM
Mica Insulators glen65 Solid State 5 22nd December 2006 07:15 PM
Mica sheets rdunnit Parts 7 10th February 2003 09:22 PM
mica plates Kilowatt Parts 1 19th November 2001 06:08 AM


New To Site? Need Help?

All times are GMT. The time now is 05:09 PM.


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