ACA JFET install Question.

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HJL857

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Joined 2009
I have just started the ACA, i am where you put the white heat sink compound on the Mica to the heat sink, My question is do you also put a layer of the white compound to the JFET POWER RESISTOR?
this is a noob question, I would appreciate anyone to chime in.
thanks much !
HJL857
 
H

HJL857

Member
Joined 2009
ACA JFET install to Heat Sink

Yes!,
Let me re-word , im following pictures instruction "I THOUGHT" : Thermo paste goes onto the under side of the MICA Fabric which is applied to the Heatsink now the Power JFET is screwed down onto the Heatsink, Then the POWER JFET is attach and soldered to the PCB marked Q1 & Q3 MY Question, should i put a thin layer of thermo paste between the topside of the MICA and the bottom side of the POWER JFET then screw it to the Heat Sink.
MEGA_amp i should have been more clear.:confused::confused::confused:
HJL857 :boggled:
 
ticktock

ticktock

Member
Joined 2006
It's so easy:

If you have soft insulators like Silicone, Kerafol or Kapton,
NO compound is required.

If you have hard insulators, you will need some compound
on both sides to fill the microscopic gaps.

Remember air is a very bad heat conductor. Any air gaps
need to be avoided.
 
H

HJL857

Member
Joined 2009
TickTock
i am getting mixed ways on how to install, it shows on the ACA build thread
actual white compound being put onto what the instructions say, Mica, IMO from the reviews of this thread its 50/50. So putting the thermal paste on both sides of the Mica
and to the bottom side of the Power JFET WILL NOT HARM THE JFET and the poulated
PCB ? .....would this be concidered over kill ?
 
MEGA_amp

MEGA_amp

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Joined 2003
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The whole purpose of the compound is to fill the microscopic air gaps. The back (metal portion) of the transistor you are mating to the heatsink is not perfectly flat; this metal portion of the transistor is also electrically connected to the Drain pin, hence why you need mica or some other electrical insulator. Apply compound on the transistor, affix mica, apply compound on the other side of the mica that meets the heataink.....like a 'mica sandwich'...the bread is the compound.


Read this:

http://www.diyaudio.com/forums/pass-labs/37262-mica-goop.html
 
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H

HJL857

Member
Joined 2009
MEGA,
Thanks for LINK and the analogie "MICA SANDWICH", and to all who helped me with this build thread.
the knowlage that comes from you guys and the Nelson Pass Diyers is so valueble to us newbie's just speaks for itself. Now i have the confidence to solder Power JFETS to the pcb Q1 & Q3. Take care , im off to a cold one and a Mica Sandwich LOL
HJL857
 
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