K3 apparent PA failure

[gfinch]

Had the same thing happen here to my K3s but only with the high power board. The low power 0 to 12 watt board continued to work normally. Tried a transmit gain calibration with no effect.
I sent it back to Elecraft and they replaced both the low and high power boards with revisions they deemed "more stable" - KPA3A Rev C9, and KLPA3A Rev B3. Greg, W1GF
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[Martin Sole-3]

Hi,

I can see output at the XVTR OUT jack. Using direct input on the LP-100A
meter it shows output varyng in sympathy with the output level control 
and a setting of L 1.00 gives pretty much 1dBm on the LP-100A. Lowest I
can read is around -12dBm and highest about +3dBm before the K3 switches
to H 0.1. Then on the main ant jack I see nothing.

I'm thinking this has to be somewhere between the input to the LPA and
the output.

Does the SWR bridge need to see some output? Just wondering if something
were fried in the the bridge so it's feeding nothing back to the
measuring circuit does that cause the PA chain to essentially shut down?

Martin, HS0ZED


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[Brian Hunt]

Have you tried doing a TX GAIN calibration?  It will likely fail given what you are seeing but it's another step to try.

GL & 73,
Brian, K0DTJ

> On Apr 9, 2018, at 18:11, Martin Sole <[hidden email]> wrote:
>
> Hi,
>
> I can see output at the XVTR OUT jack. Using direct input on the LP-100A meter it shows output varyng in sympathy with the output level control  and a setting of L 1.00 gives pretty much 1dBm on the LP-100A. Lowest I can read is around -12dBm and highest about +3dBm before the K3 switches to H 0.1. Then on the main ant jack I see nothing.
>
> I'm thinking this has to be somewhere between the input to the LPA and the output.
>
> Does the SWR bridge need to see some output? Just wondering if something were fried in the the bridge so it's feeding nothing back to the measuring circuit does that cause the PA chain to essentially shut down?
>
> Martin, HS0ZED
>

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[Martin Sole-3]

Hi,

Both output devices in the LPA, Q4 and Q5, RD15HVF-1, show low ohms gate
to source, one is 2.4 ohms the other 4.6 ohms.

Anyone have a recommended source? I don't think these are available
locally, I'll need to get a couple shipped in from US or elsewhere most
likely.

Thanks
Martin, HS0ZED

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[Matthew Cook]

Martin,

Contact Elecraft support.   I purchased a pair of the same MOSFET's a
couple of years or so ago when my K3 did the same as yours...

Unfortunately mines done it again just recently, so this time I'm ordering
a few spares.

73

Matthew
VK5ZM

On 10 April 2018 at 14:32, Martin Sole <[hidden email]> wrote:

> Hi,
>
> Both output devices in the LPA, Q4 and Q5, RD15HVF-1, show low ohms gate
> to source, one is 2.4 ohms the other 4.6 ohms.
>
> Anyone have a recommended source? I don't think these are available
> locally, I'll need to get a couple shipped in from US or elsewhere most
> likely.
>
> Thanks
> Martin, HS0ZED
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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