KNB2 Installed, but...

[L Kendall]

I built the KNB2 board and installed it today.

No problems with that, but it occurred to me while the 100 Watt board
was removed to check the TO220 packaged Q7 and Q8 on the RF board for
any electrical continuity to the heat sink .

I have to back those 4-40 nuts out to barely finger tight or it measures
short to ground.

Is there a suitable substitute material I can use for those adhesive
insulating pads between the transistor and the grounded heat sink?
Elecraft p/n in the manual is E700002.

Thanks,
Larry
K5END



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[Don Wilhelm-4]

  Larry,

You probably have some slivers of aluminum embedded in the thermal pads.
Unless you have some good thermal conductive material laying around, I
would request replacement thermal pads from [hidden email].

BTW - when you replace the hardware, do not use the internal toothed
lockwashers - they can dig out bits of aluminum and cause just the
problem you are having.  Substitute split lockwashers.  You may have
enough left over from the option installation, normally a few extras are
included.

73,
Don W3FPR

On 1/23/2011 8:43 PM, L Kendall wrote:

> I built the KNB2 board and installed it today.
>
> No problems with that, but it occurred to me while the 100 Watt board
> was removed to check the TO220 packaged Q7 and Q8 on the RF board for
> any electrical continuity to the heat sink .
>
> I have to back those 4-40 nuts out to barely finger tight or it measures
> short to ground.
>
> Is there a suitable substitute material I can use for those adhesive
> insulating pads between the transistor and the grounded heat sink?
> Elecraft p/n in the manual is E700002.
>
> Thanks,
> Larry
> K5END
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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[L Kendall]

Don, thanks.

Larry
K5END

On Sun, 2011-01-23 at 20:50 -0500, Don Wilhelm wrote:

> Larry,
>
> You probably have some slivers of aluminum embedded in the thermal pads.
> Unless you have some good thermal conductive material laying around, I
> would request replacement thermal pads from [hidden email].
>
> BTW - when you replace the hardware, do not use the internal toothed
> lockwashers - they can dig out bits of aluminum and cause just the
> problem you are having.  Substitute split lockwashers.  You may have
> enough left over from the option installation, normally a few extras are
> included.
>
> 73,
> Don W3FPR
>
> On 1/23/2011 8:43 PM, L Kendall wrote:
> > I built the KNB2 board and installed it today.
> >
> > No problems with that, but it occurred to me while the 100 Watt board
> > was removed to check the TO220 packaged Q7 and Q8 on the RF board for
> > any electrical continuity to the heat sink .
> >
> > I have to back those 4-40 nuts out to barely finger tight or it measures
> > short to ground.
> >
> > Is there a suitable substitute material I can use for those adhesive
> > insulating pads between the transistor and the grounded heat sink?
> > Elecraft p/n in the manual is E700002.
> >
> > Thanks,
> > Larry
> > K5END
> >
> >
> >
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> >

______________________________________________________________
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