4A bias on a IRFP240n??? - Page 2 - 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 19th September 2004, 11:26 AM   #11
Banned
 
Join Date: Aug 2002
Location: New York, NY
Send a message via AIM to yldouright Send a message via Yahoo to yldouright
Lars Clausen

Easily!!!???

Well, if you are going to dissipate that much heat I would suggest polishing the contact surfaces so they are are smooth and shiny as you can make them, use as thin a layer of heatsink grease as you can make (it should be barely visible except at the edges to give a visual hint) and use a variac to feed it and measure the dissipation over time. If you did a good job, the heatsinks will get hotter faster. Having a heatsink measure 70 degrees celsius is not a guarantee that the device won't fail.
  Reply With Quote
Old 19th September 2004, 12:18 PM   #12
diyAudio Member
 
Join Date: Aug 2003
Location: Prague,Czech Republic
70 C at by finger touchable parts safety norm for home electronic not permit ( not permit temperature over 60 C). You must use larger heatsink .
  Reply With Quote
Old 19th September 2004, 01:32 PM   #13
diyAudio Member
 
Join Date: Oct 2003
Location: The Lab
Upopa: You are absolutely right! However i was only discussing the safe dissipation, not safety regulation requirements.

yldouright: I agree, even if the IRFP250N may be within SOA limits, also at 100 Watts, why not take the biggest available device, at just a dollar extra cost. The IRFP260N will safely dissipate around 200 Watts at 80 C tc (what you get at 70 C heat sink temp, when mounting as proposed).
I have used a IRFP150 device as heater for years for testing heat sink values. Even with changing surfaces and loads up to 100 Watts, it has never failed.
  Reply With Quote
Old 19th September 2004, 03:23 PM   #14
sajti is offline sajti  Hungary
diyAudio Member
 
Join Date: Apr 2003
Location: Vác, Hungary
Quote:
Originally posted by Upupa Epops
70 C at by finger touchable parts safety norm for home electronic not permit ( not permit temperature over 60 C). You must use larger heatsink .
It's true, but if You put the heatsink inside the box, it can be hotter, and You can insulate it electrically from the box, and put the output device without any insulator. At 100W .2K/W insulator means 20 degree more temprature for the junction...

sajti
  Reply With Quote
Old 19th September 2004, 03:36 PM   #15
sajti is offline sajti  Hungary
diyAudio Member
 
Join Date: Apr 2003
Location: Vác, Hungary
Quote:
Originally posted by Lars Clausen
Upopa: You are absolutely right! However i was only discussing the safe dissipation, not safety regulation requirements.

yldouright: I agree, even if the IRFP250N may be within SOA limits, also at 100 Watts, why not take the biggest available device, at just a dollar extra cost. The IRFP260N will safely dissipate around 200 Watts at 80 C tc (what you get at 70 C heat sink temp, when mounting as proposed).
I have used a IRFP150 device as heater for years for testing heat sink values. Even with changing surfaces and loads up to 100 Watts, it has never failed.
Hi Lars,

I had some problem with IRFP devices on high power levels. When I put the amplifier together it works properly for few days, but after I lost it... After some investigation I found, that the I lost the mounting force, due the large temperature changes. So finally I use some more fixing for it. I never had this problem with TO-3 devices, such as IRF150.
Another issue is the fan cooling. I avoided it for long time, because it noisy. Than I tried a 12V fan with 6V DC. It runs slowly, and no noise, but reduce the heatsink temperature with 15 degree

sajti
  Reply With Quote
Old 19th September 2004, 03:50 PM   #16
diyAudio Member
 
Join Date: Aug 2003
Location: Prague,Czech Republic
To sajti : You must fit it by flexible strip and by two srews.
  Reply With Quote
Old 19th September 2004, 03:50 PM   #17
diyAudio Member
 
Join Date: Oct 2003
Location: The Lab
Sajti: Thank You for these informations
  Reply With Quote
Old 19th September 2004, 04:10 PM   #18
sajti is offline sajti  Hungary
diyAudio Member
 
Join Date: Apr 2003
Location: Vác, Hungary
Quote:
Originally posted by Upupa Epops
To sajti : You must fit it by flexible strip and by two srews.
Egzactly! I use 3mm thick steel strip, with 3 screws for two IRFPs.

sajti
  Reply With Quote
Old 20th September 2004, 09:02 AM   #19
diyAudio Member
 
Join Date: Sep 2004
Location: Kingisepp
my cooling system have four fan in amp: http://akotov.narod.ru/2.html. Power dissipation ~230watt.
  Reply With Quote
Old 20th September 2004, 09:19 AM   #20
sajti is offline sajti  Hungary
diyAudio Member
 
Join Date: Apr 2003
Location: Vác, Hungary
Quote:
Originally posted by Alex Kotov
my cooling system have four fan in amp: http://akotov.narod.ru/2.html. Power dissipation ~230watt.
Sorry, but when I click on the link, I get error message only


sajti
  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
Changing grid leak bias preamp to cathode bias bereanbill Tubes / Valves 8 28th March 2009 05:26 PM
Bias problem- 1 Socket shows extremely low bias! otokomae Tubes / Valves 12 31st December 2008 10:01 PM
Stray hum pickup *preamp* cathode R-bias vs. battery bias & 12AU7vs.5687 awedio Tubes / Valves 2 19th April 2008 01:30 AM
Battery grid bias to fixed bias in Toccato? w00t Tubes / Valves 3 2nd December 2007 12:34 AM
Supressed bias amplifier, automatic variable bias system. destroyer X Solid State 2 20th September 2004 10:24 AM


New To Site? Need Help?

All times are GMT. The time now is 05:34 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