Hi Martin;
1. It could be the relay on the KPAIO3 riser board, put it in RX and
click above and below 12W over and over to get it to fail.
2. Look at the 4 big red coils on the KPA3A... check the legs very
closely, they can break and still be touching due to the silicone.
3. Also on the newer KPA3"A", the 100ohm resistor next to the big
electrolytic runs hot and the solder crystalizes, pry gently to see if
it pops off.
It is either R19 or R5, depends of revision, replace with a 3W leaded
standing on end (see pic below).
Keith WE6R
email me for pictures my first name at elecraft.com
Here are my notes;
Poor receive RX and NO TX above 12w watts, OK below 12W.
Most likely something on KPA3, like D7,8,9 or 10. Or broken leg on one
of the big red coils.
Or; the relay on the KPAIO3 riser board. Or;
**On KPA3”A” , rev a thru C, check R5. On Rev D & E, check R19. On R5,
the pads don’t fit the resistors and some earlier resistors only have
solder on the underside at the very ends.
On both; this resistor runs hot and makes the solder underneath crystalline.
Correct part is E500486, 100 ohm 2w ,
HOWEVER, a better fix is; (February 2021-all upgraded KPA3As)
Look for heated resistor and crystalline solder under pads, just gently
pry it, it will pop off if bad;
R5 on Rev C and older,
R19 on rev D and E;
Fix: Remove surface mount 100 ohm, add E500118 100ohm 3 watt leaded as
seen in picture.
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