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KPQ100 bias adjustment

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Eugene Worth

KPQ100 bias adjustment

I'm moving on to the final alignment of my KAT100-2/KPA100 in an EC2 enclosure … split from a stock K2 …

So far, so good. Some of the testing and alignment steps are confusing since the construction assumes one wants to build the KPA100 in the K2 body. And, since I did not put a speaker into the EC2.

That said, I'm confused about the best measuring points for the bias current adjustment step on page 50 of Appendix G, Rev H KPA100 construction manual dated Sept, 2011.

I'm trying to envision exactly where to clip the probes of my DMM. I could clip the positive (red) lead to the red lead at the back of the power supply. Then the black (negative) lead to the red (+) J3 connector ???? That seems to be in parallel with the positive lead of the power cable … and the instructions clearly state in series … so, I am confused as to the best two locations to put the test leads.

After getting to this point, I would hate to goof and let magic smoke out of the radio.

Thanks in advance.

gene
WG7GW

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Don Wilhelm-4

Re: KPQ100 bias adjustment

Gene,

You must connect the DMM in series with the power supply. Remove the
positive lead from your power supply and connect the negative lead of
your DMM to the power supply terminal, then connect the positive lead of
your DMM to the + wire going to the KPA100.

The instructions are written for the normal installation where the
KPA100 is installed in place of the QRP top cover, but the same thing
applies - adjust the bias so the current increase is 400 mA.

I might suggest that you initially put the KPA100 on the K2 as called
for in the instructions. Then when all is working normally, move the
KPA100 to the EC2 enclosure; There is no need to complicate the picture
by introducing extra variables into the situation. Keep everything as
simple as possible during the "bring up" steps, and then add the
necessary complexity after those basic steps have been taken and
operation verified.

73,
Don W3FPR

On 12/1/2011 9:38 PM, Eugene Worth wrote:

> I'm moving on to the final alignment of my KAT100-2/KPA100 in an EC2 enclosure … split from a stock K2 …
>
> So far, so good. Some of the testing and alignment steps are confusing since the construction assumes one wants to build the KPA100 in the K2 body. And, since I did not put a speaker into the EC2.
>
> That said, I'm confused about the best measuring points for the bias current adjustment step on page 50 of Appendix G, Rev H KPA100 construction manual dated Sept, 2011.
>
> I'm trying to envision exactly where to clip the probes of my DMM. I could clip the positive (red) lead to the red lead at the back of the power supply. Then the black (negative) lead to the red (+) J3 connector ???? That seems to be in parallel with the positive lead of the power cable … and the instructions clearly state in series … so, I am confused as to the best two locations to put the test leads.
>
> After getting to this point, I would hate to goof and let magic smoke out of the radio.
>
> Thanks in advance.
>
> gene
> WG7GW
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

______________________________________________________________
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Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html

Eugene Worth

Re: KPQ100 bias adjustment

Thanks of Don and Ron!

I've got the picture now.

gene
WG7GW

On Dec 1, 2011, at 9:57 PM, Don Wilhelm wrote:

> Gene,
>
> You must connect the DMM in series with the power supply. Remove the positive lead from your power supply and connect the negative lead of your DMM to the power supply terminal, then connect the positive lead of your DMM to the + wire going to the KPA100.
>
> The instructions are written for the normal installation where the KPA100 is installed in place of the QRP top cover, but the same thing applies - adjust the bias so the current increase is 400 mA.
>
> I might suggest that you initially put the KPA100 on the K2 as called for in the instructions. Then when all is working normally, move the KPA100 to the EC2 enclosure; There is no need to complicate the picture by introducing extra variables into the situation. Keep everything as simple as possible during the "bring up" steps, and then add the necessary complexity after those basic steps have been taken and operation verified.
>
> 73,
> Don W3FPR