[Elecraft] KPA100 bias issues...

[Don Wilhelm]

Steve,

Rotate the KPA100 bias pot back to its full counterclockwise position, 
make certain you have a good dummy load on the KPA100, and then try the 
steps below:

First, determine if the current draw at 0.1 watts is high in the base K2 
or the KPA100.
Disconnect the ribbon cable to the KPA100 and measure the current draw - 
expect 240ma to 360 ma - this will depend on how many options you have 
installed - low end if you have no options and high end if your K2 has a 
full house (especially the KDSP2).  If you have considerably more 
current draw than that, re-look at the base K2 for the cause.

If your current draw is within range, power off and install the ribbon 
cable - the KPA100 will add some to the current draw found in the above 
step - expect 50 to 100 ma more..

Now turn the power up to 11 watts or higher - the current should 
increase another 100 to 150 ma depending on the state of the fan.

When all the above is within range, put the K2 into CW TEST - that is 
very important.

Add 400 ma to whatever the current draw was in the above 11+ watt check 
- that is your desired final bias current setting.

Now press TUNE - at first the current will not increase very much, but 
with rotation of the bias pot, the current should increase.  Find the 
place where the current increases about 400 ma and stop for now - you 
are close.

Go out of  TUNE by tapping any button - do not power off or you will 
lose the CW TEST condition
(that is why you received the HI REFL message).

Enter TUNE and quickly check the current draw and exit TUNE.  The 
current draw will climb after a half second or so, but the initial 
reading on your DMM may be too low because the gate timing on your DMM 
is not synchronized, so look at the reading for the second scan - in 
other words wait more than a tenth of a second and less than half a 
second to see the correct reading.

If the reading is too low adjust the pot slightly clockwise, but if it 
is too high, adjust it a tiny bit in the counterclockwise direction.

73,
Don W3FPR

Steve Kallal wrote:
> I have progressed through the KPA100 adjustments with NO issues until I got
> to the bias adjustments on pages 49 and 50. I am unable to get any current
> reading changes when adjusting R6. First of all, my current drain at 0.1
> watts is about 500 mA rather than the 200 to 400 mA mentioned in the manual.
> When I go into TUNE mode and set the power to 11 watts, the current drops to
> about 600 mA and there is NO current change when adjusting R6. There are two
> errors that pop up on the LCD display. First it displays HI REFL and then PA
> HOT. I went back and double checked my TPA and SWR settings from the
> previous section. All is OK.
>
>
>