KPA100 Update

[Roy Morris-6]

I have one of the older KPA100s and have done all the mods and upgrades.  However, I have seen a recommendation to change C80 and C81 from 4700 to 5600.   I have not seen these cap changes in the errata sheets.  My KPA100 works well on all bands, 160 thru 10 (including 60 meters) with full output on all bands.  Are the new KPA100 kits supplying the 5600s or are these just changes if there is a problem with 15 and 17 meter low output?  Thanks   Roy Morris  W4WFB
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[Vic K2VCO]

Roy Morris wrote:
> I have one of the older KPA100s and have done all the mods and
> upgrades.  However, I have seen a recommendation to change C80 and
> C81 from 4700 to 5600.   I have not seen these cap changes in the
> errata sheets.  My KPA100 works well on all bands, 160 thru 10
> (including 60 meters) with full output on all bands.  Are the new
> KPA100 kits supplying the 5600s or are these just changes if there is
> a problem with 15 and 17 meter low output?  

As I understand it, there is no reason to make this change if you do not
have low output on 20/17 meters.

The gain of the KPA100 varies over the frequency range, and dips
somewhere near the 30/20/17 meter bands.  On some KPA100s this dip is
deep enough to make it hard for the driver to supply enough drive for
full output.  There's been a lot of discussion about the exact cause of
this dip, but according to Elecraft this change fixes a problem caused
by capacitors that are at the low extreme of their tolerance range.

--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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[Don Wilhelm-3]

Morris,

If your KPA100 works FB, do not change anything.

I have it on good authority that the real problem is not the capacitors, but
the resistors, particularly the 1.6 ohm 2 watt resistors.  Apparently the
manufacturer changed to an inductive design without consulting with their
clients (including ELecraft).  As a result, you can look for Builder's alert
22 to be resinded and replaced with a new one.

Again, if your KPA100 has good output on all bands, this is NOT for you - it
only happens to those unlucky folks who received resistors that are
inductive with their kit - the older resistors are non-inductive, and no
change is recommended - 'If it ain't broke, don't fix it'.

73,
Don W3FPR

> -----Original Message-----
>
> I have one of the older KPA100s and have done all the mods and
> upgrades.  However, I have seen a recommendation to change C80
> and C81 from 4700 to 5600.   I have not seen these cap changes in
> the errata sheets.  My KPA100 works well on all bands, 160 thru
> 10 (including 60 meters) with full output on all bands.  Are the
> new KPA100 kits supplying the 5600s or are these just changes if
> there is a problem with 15 and 17 meter low output?  Thanks   Roy
> Morris  W4WFB
>

--
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