KX1 Problem with TX

[Gerald Eberle]

I've built my KX1 #2203 a while ago and it was working well. After adding 30/80m there was low output from time to time which I found out had to do with the LP-Filter-board.
So, these days I wanted to fix that and thereby caused some smoke, around Q6 I guess. Probably tuned the TX to long to put the windings in place on the Filter-board.
After that, every time switching on the KX1 caused a short somewhere and switched off the Powersupply. So, no Power no chance to measure something.
Then I removed Q6 and the RX is working again like nothing has been broken. The original Q6 seems to be dead but everything else looks ok including D7.
Using a temporary BD136 as Q6 causes high current and it gets burning hot. There seems to be a short somewhere.
Where should I start to catch the fault? Any ideas are welcome. Thanks in advance.
73, Gerald

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[Don Wilhelm-4]

Gerald,

 From your description, I would strongly suggest that you order a
2SC2166 or two from Elecraft.
If you are attempting to operate the KX1 without a heatsink on Q6, DO
NOT DO THAT.  Q6 will be zapped in very short order.  Use a heat sink on
Q6 at all times.

73,
Don W3FPR

On 3/24/2012 7:12 AM, Gerald Eberle wrote:
> I've built my KX1 #2203 a while ago and it was working well. After adding 30/80m there was low output from time to time which I found out had to do with the LP-Filter-board.
> So, these days I wanted to fix that and thereby caused some smoke, around Q6 I guess. Probably tuned the TX to long to put the windings in place on the Filter-board.
> After that, every time switching on the KX1 caused a short somewhere and switched off the Powersupply. So, no Power no chance to measure something.
> Then I removed Q6 and the RX is working again like nothing has been broken. The original Q6 seems to be dead but everything else looks ok including D7.
> Using a temporary BD136 as Q6 causes high current and it gets burning hot. There seems to be a short somewhere.
> Where should I start to catch the fault? Any ideas are welcome. Thanks in advance.
> 73, Gerald
>
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[Gerald Eberle]

Hello Don, thanks for your fast reply.
I meant a BD139 not BD136 of course, and I had mounted a small heatsink, but maybe that was to small.
So I will take your advice and get the original type as a replacement of Q6 and see how that works.
73, Gerald
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