KPA100 HELP!!!

[Chris Hurlbut]

I posted a couple months ago with a problem I am having with my KPA100.  
Life has gotten in the way, and I didn't get fully through the
solution.  Someone, I think an N9?, was helping me, but I had a HD crash
and lost those emails.

The short story is a screwdriver was dropped into the open K2/100 during
final testing stages, just before I got to the bias adjustment.  Things
sparked real pretty like, and the K2 no longer recognized the KPA100.

I replaced U2, U4, and U5 (I think that's right.) I also replaced Q6,
Q7, Q10, Q11, Q12 and R8.

The K2 now sees the KPA100 well enough to give me error code E12 and
Firmware version 1.10.  I can't get the K2 to see that the high power
12V supply is plugged into the KPA100.   I always get a NO PA PS
message, hence the E12 error.

I get 13.8V into R8, and 0.8V out of it.  Then I get 13.8V into Q12, and
0.8V out.  Thus, Pin 7 of U1 only has 0.8V.  The manual says it needs
4V, and I can't find a 4V reading on anything, anywhere.

The K2 turns on just fine with *just* the high power 12V supply plugged in.

Any ideas, anyone?  I really want to get this thing going!

Thanks,
-Chris KL9A
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[Don Wilhelm-3]

Chris,

To summarize the circuit, the level at the U1 input pin 7 tells the KPA100
uP whether the power supply is present.  When the 12CTRL line is active
(this comes from power on in the base K2) at the gate of Q12, Q12 will
conduct from the drain to the source, and R8 and the resistor between pins 5
and 6 of RP1 form a voltage divider to place about 4 volts on pin 7 of U1.

So your problem can be found as one of the following:
Shorted pin 7 input to U1 (most likely)
Shorted resistor on RP1 (somewhat likely)
Open R8 (somewhat likely)
Short ot ground at Q12 or somewhere on the PC board trace (less likely)

With power off, make some resistance readings. (These are sequential steps,
proceed only until you have a sensible reading and then STOP and fix the
problem).

Measure the resistance across R8, it should be 10k - if much higher replace
R8.

>From Q12 source to ground you should measure just a bit less than 3.9k, if
it is substantially less than that, remove U1 and remeasure.  If still less,
unsolder Q12 - if still less than 3.9k remove RP1, there will be nothing
remaining connected to the PC trace, so if it still is low resistance, look
for the short on the board.

Those steps should correct the NO PA PS problem.

73,
Don W3FPR


> -----Original Message-----

> The short story is a screwdriver was dropped into the open K2/100 during
> final testing stages, just before I got to the bias adjustment.  Things
> sparked real pretty like, and the K2 no longer recognized the KPA100.
>
> I replaced U2, U4, and U5 (I think that's right.) I also replaced Q6,
> Q7, Q10, Q11, Q12 and R8.
>
> The K2 now sees the KPA100 well enough to give me error code E12 and
> Firmware version 1.10.  I can't get the K2 to see that the high power
> 12V supply is plugged into the KPA100.   I always get a NO PA PS
> message, hence the E12 error.
>
> I get 13.8V into R8, and 0.8V out of it.  Then I get 13.8V into Q12, and
> 0.8V out.  Thus, Pin 7 of U1 only has 0.8V.  The manual says it needs
> 4V, and I can't find a 4V reading on anything, anywhere.
>
> The K2 turns on just fine with *just* the high power 12V supply
> plugged in.
>
> Any ideas, anyone?  I really want to get this thing going!
>
> Thanks,
> -Chris KL9A
>

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