KPA100 Thermal Pads

[Anthony Bowyer]

  I need to replace the speaker in a k2/100, but it
requires that the KPA100 PA transistors and the board
be removed from the heatsink.

  Anyone aware of any issues with reusing the thermal
pads?

  I really like thermal grease better, but since this
is what it was built with, I'll stick with it. Just
not sure if their effectiveness is dimished when
reused.

Thank you,
Anthony, NT4X  


       
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[Ron D'Eau Claire-2]

My KPA100 has been apart many, many times, documenting various mods and
upgrades for Elecraft. The first time I took it apart, the pads tore, with
some parts sticking to the transistors and other parts sticking to the
heatsink. It had been assembled and had many hours of very heavy operation
and testing often raising the heat sink temp too much to want to leave my
hand on it, so I wasn't surprised the pads were well bonded to the surfaces.
The tearing wasn't a problem. When the heat sink was fitted to the
transistors again, the sections of pads fit together to form a complete pad.


I guess it was after about dozen such separations and reinstallations that I
finally damaged the part of a pad stuck to a transistor while working on the
unit, so I replace them both.

Ron AC7AC

-----Original Message-----



  I need to replace the speaker in a k2/100, but it
requires that the KPA100 PA transistors and the board
be removed from the heatsink.

  Anyone aware of any issues with reusing the thermal
pads?

  I really like thermal grease better, but since this
is what it was built with, I'll stick with it. Just
not sure if their effectiveness is dimished when
reused.

Thank you,
Anthony, NT4X  

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[Don Wilhelm-3]

Anthony,

You can reuse the KPA100 thermal pads unless they are obviously torn in
such a way that they will not go back in place.  They usually stick to
either the transistor or the heat sink - take care not to damage or
disturb their relative positions when working on the KPA100 board and
all will be well.

If you do replace the thermal pads, I would recommend that you follow
the re-tightening procedure after about 20 hours of operation at high
power - the new pads need time and heat to conform the the transistors
and the heat sink.  If you re-use the old ones, you will not have to do
the re-tightening.

Heat sink compound is not only messy, but for some compounds, the heat
sink pads supplied by Elecraft conduct heat much better.  Use heat sink
compound only at your own peril (replacement transistors are about $68 <G>).

73,
Don W3FPR

Anthony Bowyer wrote:

>   I need to replace the speaker in a k2/100, but it
> requires that the KPA100 PA transistors and the board
> be removed from the heatsink.
>
>   Anyone aware of any issues with reusing the thermal
> pads?
>
>   I really like thermal grease better, but since this
> is what it was built with, I'll stick with it. Just
> not sure if their effectiveness is dimished when
> reused.
>
> Thank you,
> Anthony, NT4X  
>
>
>        
> ____________________________________________________________________________________
> Moody friends. Drama queens. Your life? Nope! - their life, your story. Play Sims Stories at Yahoo! Games.
> http://sims.yahoo.com/ 
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft   
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>

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