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K2/100 power output

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wsm-3

K2/100 power output

Hello

My K2/100 just recently started going to 100 watts output
as soon as I set the output to 11 watts or greater.
I disconnected the amp, and am back to the qrp version and
everything works fine. So I asume the problem is with the
amp. Am I correct?
Thanks
Scott N5SM

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Don Wilhelm-4

Re: K2/100 power output

Scott,

Yes, the problem is with the KPA100. The most likely thing is that
diodes D16 and D17 are damaged which results in the KPA100 not being
able to tell the K2 that power output is being developed, so the K2 just
increases the power to the max in an effort to obtain a power output
indication. At setting less than 11 watts, the base K2 is probably
producing its maximum power output as well which will be in the 10 to 15
watt range.

The most probable cause for D16, D17 failure is a lightning surge - it
is always a good idea to disconnect the antennas when not in use. I
switch all my equipment to a dummy load unless I am actively operating.

73,
Don W3FPR

[hidden email] wrote:

> Hello
>
> My K2/100 just recently started going to 100 watts output
> as soon as I set the output to 11 watts or greater.
> I disconnected the amp, and am back to the qrp version and
> everything works fine. So I asume the problem is with the
> amp. Am I correct?
> Thanks
> Scott N5SM
>
>
> _______________________________________________
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Matt Zilmer

K3 - RF board: Q2 leakage

Hi Don,

A few K3 firmware revs ago, after I updated the radio, I noticed some
strange power on behavior. I was in touch with Wayne at the time on
another subject, and he indicated these symptoms indicate a high
leakage on Q2 - RF board.

Symptoms:
Rapid-firing the Power switch only lights up the LCD backlight. If
one cycles the external power supply between K3 power cycles, this
doesn't happen. If I can get the K3 to sequence power up normally,
there is a _loud_ period of audio that sounds muffled, like it's on
the wrong filter setting or there is something going on with the RX
EQ. After the strange audio disappears, things seem to go normally.

I never noticed these symptoms before, so I though there was some
change in the new firmware I loaded. Wayne thought otherwise, and
suggested that the symptom indicated Q2 had excess leakage.

Power supply below is set at 13.8VDC.

DVM time:
K3 power off, with external power applied -
Q2-G - 13.3V
Q2-D - 0.097V

K3 power on -
Q2-G: 6.66V
Q2-D: 13.3V

So far so good. But watching Q2-D while powering down, it takes
between 2 and 4 seconds for that net to drop from full voltage output
to about 0.5V. Wayne had said that high leakage would be indicated by
a slow retreat of the drain voltage from full output to about 0.5V.

On the other hand, I don't know if the 0.1V that shows at Q2-D while
the K3 is powered off is right or not. That would indicate a static
leakage value to me. I think it should be *a lot* closer to 0V.

I have a replacement Q2 here, but don't want to "operate" on the radio
unless it's really necessary. Do you have any recommendations?

Thanks,
Matt Zilmer, W6NIA
K3 #24
K2 #2810

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Don Wilhelm-4

Re: K3 - RF board: Q2 leakage

Matt,

Wayne have more intimate knowledge of the K3 hardware and MCU firmware
than anyone else. If Wayne believes that replacing Q2 will fix the
problem, then I would replace Q2.

73,
Don W3FPR

Matt Zilmer wrote:

> Hi Don,
>
> A few K3 firmware revs ago, after I updated the radio, I noticed some
> strange power on behavior. I was in touch with Wayne at the time on
> another subject, and he indicated these symptoms indicate a high
> leakage on Q2 - RF board.
>
> Symptoms:
> Rapid-firing the Power switch only lights up the LCD backlight. If
> one cycles the external power supply between K3 power cycles, this
> doesn't happen. If I can get the K3 to sequence power up normally,
> there is a _loud_ period of audio that sounds muffled, like it's on
> the wrong filter setting or there is something going on with the RX
> EQ. After the strange audio disappears, things seem to go normally.
>
> I never noticed these symptoms before, so I though there was some
> change in the new firmware I loaded. Wayne thought otherwise, and
> suggested that the symptom indicated Q2 had excess leakage.
>
> Power supply below is set at 13.8VDC.
>
> DVM time:
> K3 power off, with external power applied -
> Q2-G - 13.3V
> Q2-D - 0.097V
>
> K3 power on -
> Q2-G: 6.66V
> Q2-D: 13.3V
>
> So far so good. But watching Q2-D while powering down, it takes
> between 2 and 4 seconds for that net to drop from full voltage output
> to about 0.5V. Wayne had said that high leakage would be indicated by
> a slow retreat of the drain voltage from full output to about 0.5V.
>
> On the other hand, I don't know if the 0.1V that shows at Q2-D while
> the K3 is powered off is right or not. That would indicate a static
> leakage value to me. I think it should be *a lot* closer to 0V.
>
> I have a replacement Q2 here, but don't want to "operate" on the radio
> unless it's really necessary. Do you have any recommendations?
>
> Thanks,
> Matt Zilmer, W6NIA
> K3 #24
> K2 #2810
>
>