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Old 5th May 2016, 06:03 AM   #41
sangram is offline sangram  India
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The difference between 200 and 300 is the efficiency of a linear supply. As such, both figures are absolutely correct.
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Old 5th May 2016, 07:29 AM   #42
el_mariachi is offline el_mariachi  Norway
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Quote:
Originally Posted by 2 picoDumbs View Post
(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 View Post

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.

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Old 5th May 2016, 08:51 AM   #43
2 picoDumbs is offline 2 picoDumbs  Australia
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Tj is not 116. That was a simple calculator mistake.
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Old 5th May 2016, 09:25 AM   #44
el_mariachi is offline el_mariachi  Norway
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Quote:
Originally Posted by 2 picoDumbs View Post
Tj is not 116. That was a simple calculator mistake.

I tought this was the calculator mistake:


Quote:
Originally Posted by Nelson Pass View Post
Yes, should have been +25, and old calculator.

(me)

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Old 5th May 2016, 11:01 AM   #45
2 picoDumbs is offline 2 picoDumbs  Australia
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Yeah that was another one.

64 + 25 = 89
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Old 5th August 2017, 12:13 PM   #46
2 picoDumbs is offline 2 picoDumbs  Australia
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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.
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Old 5th August 2017, 12:55 PM   #47
AndrewT is offline AndrewT  Scotland
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I think it was EUVL that did a comparison in one of his papers attached to the F5x Thread.
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Old 5th August 2017, 12:59 PM   #48
AndrewT is offline AndrewT  Scotland
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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.
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Old 5th August 2017, 01:05 PM   #49
2 picoDumbs is offline 2 picoDumbs  Australia
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This is the sought of thing I have observed also.
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Old 10th October 2018, 11:23 PM   #50
astromo is offline astromo  Australia
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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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