Re: K3-100/KPA500 High SWR on 80 Meters Only

Bob McGraw - K4TAX

The first unit failed in April 2018 after some 2 years of satisfactory operation.  The second unit failed within about a week of replacement.  The radio was sent to Elecraft in May 2018.  They replaced the KPA3A.   During the first 2 years of operating I was driving an AL-80B at 60 to 70 watts.   That amp was replaced in April 2018 with a new factory  assembled KPA500.  That is when the issue and failures started. 

At the advice of others, I have either operated the radio at 10 watts to drive my KPA500 to about 250 watts or at 20 watts to drive the KPA500 to 450 to 550 watts.   I have avoided operating the radio in the 12 to 15 watt power range.  From previous experience, I did initially operate the radio in this range with the new KPA500.   The last KPA3A replaced by Elecraft in May 2018 is alive and well.   The Service report indicates that it is a "stable Rev E amp". 


Bob, K4TAX

On 10/28/2018 9:46 PM, Randy Farmer wrote:
I don't know the S/N range for the problem PA modules. Mine is 10175 (kit), so yours and mine were probably manufactured at about the same time early in the K3S production run. The factory folks can probably give you the details. Did all of your KPA3As have the same problem? My replacement unit cured the problem and it hasn't returned.

Randy, W8FN

On 10/28/2018 9:39 PM, Bob McGraw - K4TAX wrote:


Do you have any Serial Number Range of units affected?   I've been through 2 KPA3A assemblies, with the 3rd now in the radio since May of this year.  The radio was purchased new from Elecraft in August 2015.  The serial number is 10163.

Bob, K4TAX

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