Arrgh! I put 12volts into K3 antenna connector!

[Elecraft mailing list]

I accidentally hooked up a bias tee (DC power injector) backwards, which  put +12V into the K3's antenna connector. The results were not good: a burning smell from the rear of radio. The radio was in QRP mode (<10watts, so PA bypassed?) on 40m when it happened.

RX appears to be fine. The radio still makes 100W out, but the SWR reads 99.9 on all bands (into a dummy load).  Also, the power control has no effect - power out is always 100W.

Looking at the schematic, T4 in the SWR bridge certainly would have been fried by applying 12V to the antenna connector.

What else did I damage?

KevinK6TOP

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[n4kd]

Hi Kevin,
The same thing happened to me when a bias-t failed. The damage was limited to the SWR circuitry. If I recall, T4 was replaced and a burnt trace on the pcb was repaired.

- 73,
Dave N4KD

> On Mar 26, 2021, at 00:48, Kevin McGrath via Elecraft <[hidden email]> wrote:
>
> I accidentally hooked up a bias tee (DC power injector) backwards, which  put +12V into the K3's antenna connector. The results were not good: a burning smell from the rear of radio. The radio was in QRP mode (<10watts, so PA bypassed?) on 40m when it happened.
>
> RX appears to be fine. The radio still makes 100W out, but the SWR reads 99.9 on all bands (into a dummy load).  Also, the power control has no effect - power out is always 100W.
>
> Looking at the schematic, T4 in the SWR bridge certainly would have been fried by applying 12V to the antenna connector.
>
> What else did I damage?
>
> KevinK6TOP
>
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> Elecraft mailing list
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[KeithWE6R]

Hi Kevin;
If it is a K3"S" there is a trace on the bottom of the board that burns
before T4 cooks. A simple jumper will fix.
If K3, then T4 is probably cooked. There is also a loop of insulated
wire that goes up and over and down thru T4.(awkward, but probably OK).
Take the top cover off, you can look down there next to the KAT3 or
KANT3 board to asses.
We have some T4s in the Tech-parts area, when you order, you may need to
tell them to look there.
Our # is E690126
Keith WE6R Elecraft K3/K4 Tech


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