K2/KPA100 power adjustment problem

[Jess Gypin]

Hi all,
I finally got the last part into the KPA100. It was missing C71. After
pulling the board out and installing the cap, now I am not getting any power
adjustment at low power or high power. With the KPA100 removed, the power
adjustment is fine. The low power adjustment goes from about .1 watt to
about 12 watts. With the KPA100 installed, the RF out display still shows
that the power should be adjustable, but the low power output, below 11
watts, is maxed out with no lowering or adjustment of power. Above 11 watts,
power output is full 100+ watts with no adjustment. Has anyone got any tips
on where to start looking?

Also, have connected the serial cable after getting it built, turned on the
K2IO in the menu PORT function, but it appears that I am not communicating
with the K2 at all. No test characters when using HyperTerminal and no
control using various K2 software programs. Would also like some tips on
where to start the troubleshooting of this problem. I have checked the
cable, know it is wired right according to the directions using 2-2, 3-3 and
5-5 with the hardware loop installed. Also know that my computer is fine
because I use it to run my FT817 with Ham Radio Deluxe.

Jess AE0CW


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[Don Wilhelm-3]

Jess,

The real answer to your problem is that the KPA100 wattmeter is not
producing voltage onto the VRFDET line back to the base K2.

Look at the schematic sheet 1 of 2 and you will find the wattmeter and the
circuits that develop the VRFDET signal on the upper right side of that
diagram.  Check each one of them for proper soldering.

Specifically check T4 to be certain all 6 leads are proper - leads 1 and 3
should be the same color and leads 2 and 4 should be the other color.  The
red wire from the SO239 should go through the center of the toroid and the
bare wire from the SO239 should be in hole 6.

Check the diodes for proper orientation.

Transmit at high power briefly while checking the voltage at the ungrounded
end of R26 - you should find more than 4 volts if T4 and the diodes are
doing their job correctly.  If you have litle or no voltage there, the
problem is in T4 and its associated components, but if you have good voltage
at the top of R26, look for the problem in active devices that feed the
VRFDET signal.

The voltage at pins 5, 6 and 7 of U5 should all be the same.
If you have a significant voltage at U6 pin 3 during transmit periods, but
none at U6 pin 6, then check the voltage at U6 pin 8 - it should be near 5
volts during transmit.

Tackle the computer link problem after you get the power control tamed.

Let us know what you find.

73,
Don W3FPR

> -----Original Message-----
>
> Hi all,
> I finally got the last part into the KPA100. It was missing C71. After
> pulling the board out and installing the cap, now I am not
> getting any power
> adjustment at low power or high power. With the KPA100 removed, the power
> adjustment is fine. The low power adjustment goes from about .1 watt to
> about 12 watts. With the KPA100 installed, the RF out display still shows
> that the power should be adjustable, but the low power output, below 11
> watts, is maxed out with no lowering or adjustment of power.
> Above 11 watts,
> power output is full 100+ watts with no adjustment. Has anyone
> got any tips
> on where to start looking?
>
> Also, have connected the serial cable after getting it built,
> turned on the
> K2IO in the menu PORT function, but it appears that I am not communicating
> with the K2 at all. No test characters when using HyperTerminal and no
> control using various K2 software programs. Would also like some tips on
> where to start the troubleshooting of this problem. I have checked the
> cable, know it is wired right according to the directions using
> 2-2, 3-3 and
> 5-5 with the hardware loop installed. Also know that my computer is fine
> because I use it to run my FT817 with Ham Radio Deluxe.
>
> Jess AE0CW
>
>

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