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 5th May 2016, 06:03 AM #41 sangram   diyAudio Member   Join Date: Sep 2002 Location: India The difference between 200 and 300 is the efficiency of a linear supply. As such, both figures are absolutely correct.
el_mariachi
diyAudio Member

Join Date: Mar 2006
Location: highlands
Quote:
 Originally Posted by 2 picoDumbs (89-25)/4 = 16 12 × 16 = 192W Zen Mod was being a funny man. 42 is the answer to life, the universe, and everything.
I was almost able to understand Zen Mod's joke

But in the example (below) there is a difference between:

TJ=16 * (1 + 1 + 2) +25

and TJ = 116

16 * 4 + 25 = 89

But Tj is 116

116 - 89 = 27

And now i can't sleep, what is this 27 and where did it come from?

Quote:
 Originally Posted by Nelson Pass In our Aleph 2 example Tj = 16 * (1 + 1 + 2) -25 Tj = 116 deg C. And this is why Aleph 2's don't break.

 5th May 2016, 08:51 AM #43 2 picoDumbs   diyAudio Member     Join Date: Sep 2013 Tj is not 116. That was a simple calculator mistake. __________________ "If you leave this point unattached to some circuitry, an ideal constant current source will emit a small lightning bolt which will travel until it connects to something." Nelson Pass
el_mariachi
diyAudio Member

Join Date: Mar 2006
Location: highlands
Quote:
 Originally Posted by 2 picoDumbs Tj is not 116. That was a simple calculator mistake.

I tought this was the calculator mistake:

Quote:
 Originally Posted by Nelson Pass Yes, should have been +25, and old calculator. (me)

 5th May 2016, 11:01 AM #45 2 picoDumbs   diyAudio Member     Join Date: Sep 2013 Yeah that was another one. 64 + 25 = 89 __________________ "If you leave this point unattached to some circuitry, an ideal constant current source will emit a small lightning bolt which will travel until it connects to something." Nelson Pass
 5th August 2017, 12:13 PM #46 2 picoDumbs   diyAudio Member     Join Date: Sep 2013 Keratherm claim the thermal resistance (Rth) of their red 86/82 thermal pads is around 0.1 K/W. http://www.kerafol.com/fileadmin/use...r_TM_86_82.pdf Has anyone had a chance to confirm it? I did a quick comparison verse generic silcone thermal pads and the keratherm pads are significantly better. __________________ "If you leave this point unattached to some circuitry, an ideal constant current source will emit a small lightning bolt which will travel until it connects to something." Nelson Pass
 5th August 2017, 12:55 PM #47 AndrewT   R.I.P.   Join Date: Jul 2004 Location: Scottish Borders I think it was EUVL that did a comparison in one of his papers attached to the F5x Thread. __________________ regards Andrew T.
AndrewT
R.I.P.

Join Date: Jul 2004
Location: Scottish Borders
Quote:
 I did a quick comparison verse generic silcone thermal pads and the keratherm pads are significantly better.
I reported an anomaly a few years ago when in the testing phase of a paralleled output stage of a power amplifier.
I ran out of plastic/silicone insulators and used some thin mica to complete the test assembly.
The currents through the various paralleled devices were very different !
It was the lower temperature of the mica mounted insulators that caused the Vbe to be higher and this reduced the current in the mica mounted devices.
The silicone mounted devices thus had to pass a higher proportion of the current and as a result had to run even hotter, exaggerating the unbalance.
Changing to all mica mounted removed the unbalance in the 3pair output stage.
__________________
regards Andrew T.

 5th August 2017, 01:05 PM #49 2 picoDumbs   diyAudio Member     Join Date: Sep 2013 This is the sought of thing I have observed also. __________________ "If you leave this point unattached to some circuitry, an ideal constant current source will emit a small lightning bolt which will travel until it connects to something." Nelson Pass
 10th October 2018, 11:23 PM #50 astromo   diyAudio Member   Join Date: Nov 2017 Location: BFN Thanks Nelson. Setting out this detail clears up a few unknowns for me. Equations work for me. I may not be an Elec Eng but heat transfer is part of what I do.

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