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Old 21st September 2018, 09:17 PM   #351
Zen Mod is offline Zen Mod  Serbia
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it doesnt't matter what type of thermal interface you have - you need to get rid of , say , 100W of heat ...... do not forget poor small mosfet ....... keratherm T0247 pad is sorta necessary to keep it well and alive

so , heatsink need to be of proper and healthy performance

SIT is so damn big , so even cheap and crude thermal interface will do the job , contrary to mosfet side
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Old 21st September 2018, 10:15 PM   #352
plasnu is offline plasnu  United States
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Quote:
Originally Posted by Soundhappy View Post
1|
top notch quality arctic silver goop and large keratherm sheet = $$
with moderate size heat sink ?
I believe that Arctic Silver is electrically conductive. I had to replace it with Arctic Alumina...
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Old 21st September 2018, 11:34 PM   #353
dewdrop is offline dewdrop  Singapore
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Quote:
Originally Posted by Zen Mod View Post
it doesnt't matter what type of thermal interface you have - you need to get rid of , say , 100W of heat ...... do not forget poor small mosfet ....... keratherm T0247 pad is sorta necessary to keep it well and alive

so , heatsink need to be of proper and healthy performance

SIT is so damn big , so even cheap and crude thermal interface will do the job , contrary to mosfet side
ZM, 100W per channel? Without a fan, will a 4U chassis work?
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Old 22nd September 2018, 05:58 AM   #354
dBel84 is offline dBel84  United States
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Quote:
Originally Posted by Zen Mod View Post
for THF51-S .....having gate voltage in range of -1 to -3V6 is adequate for SissySIT circuit
Interesting findings when I measured my THF51-S tonight

The 2 I bought from Pras measure VGS = -3.4 and -3.5 respectively for Iq of 1A8 at 19V while the 2 I got from Tomo measure -1.8 and -1.6 at the same current and drain voltage.

Happy Days are coming ..dB
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Old 22nd September 2018, 06:06 AM   #355
pras1170 is offline pras1170  China
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Default THF-51S

Quote:
Originally Posted by dBel84 View Post
Interesting findings when I measured my THF51-S tonight

The 2 I bought from Pras measure VGS = -3.4 and -3.5 respectively for Iq of 1A8 at 19V while the 2 I got from Tomo measure -1.8 and -1.6 at the same current and drain voltage.

Happy Days are coming ..dB
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Old 22nd September 2018, 07:29 AM   #356
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by dewdrop View Post
ZM, 100W per channel? Without a fan, will a 4U chassis work?
100W of heat per channel , nominally

say that you have 22V5dc rails , and 2A Iq , that's 45V x 2A = 90W of heat

Modushop's Pesante Dissipante 4U/400 is swiss knife solution for FW amps format

enough meat to cool it off , enough space for dual mono , if you choose it

4U/300 is ...... sorta FW amp in iPod case

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Old 22nd September 2018, 10:56 AM   #357
dewdrop is offline dewdrop  Singapore
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Purrfect then ;-)
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Old 22nd September 2018, 07:09 PM   #358
Soundhappy is offline Soundhappy  France
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Quote:
Originally Posted by Zen Mod View Post
SIT is so damn big , so even cheap and crude thermal interface will do the job , contrary to mosfet side
For TO-247 mosfet clamp can do case thermal extension or better solution not clamp but small heat sink on external side. This one on the right photo is TO-220 format show only for example
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Old 22nd September 2018, 07:13 PM   #359
Zen Mod is offline Zen Mod  Serbia
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that's gilding the lily ......... hey , but what's hobby without that ?

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Old 23rd September 2018, 01:05 AM   #360
Ben Mah is offline Ben Mah  Canada
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I have been in discussions with watanabetomoaki of ebay regarding the Vgs measurements of the THF-51S that I had purchased from him. His test method was different from the one shown by Zen Mod. He has asked me to pass on the following message:

"I have been requested only by SIT of the same characteristics from many members of this forum. Thank you.
I did not include such strict matching fee for my listing, but at first I was receiving favorably.
However, too many people made the same request, and even complaints about the accuracy of screening came.
In this state, in the near future I will not be able to continue similar services.
Anyway, no so much stock anymore ...
However, I also made a mistake. That is, there are several sorted by connecting drain and source in reverse.
That was happend when the buyer directly requested the determined Id value.
In principle, the FET has no polarity at drain and source. Of course, this FET does not have built-in protection diodes like MOS type ones.
So, drain and source may be either. So, why do you specify it? That is because, of course, the value of Id is not symmetrical at all.
Naturally, as a manufacturing company, because typical characteristics are shown, general polarity designation is necessary.
However, there is no necessity for measuring the characteristics data sheet with DIY and using it.
So, in order to get closer to the Id value that the purchaser wished, the person who specified the Id value,I have measured the metal case as GND.
I think that it is my only mistake to have a case where I forget to tell him that.
So, if you received the SITs those characteristics are very different, measure the drain and source by exchanging it and use it."
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