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Re: K2 Build #7552 Progress

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Kev Schache

Re: K2 Build #7552 Progress

I have now completed up to the start of Assembly, Part III, P67, with
all tests and alignments done.
AND BEST OF ALL, it works!! I have actually heard several strong SSB
signals on 40M...... YAAYY!!

Although I am limited with test equipment, I've managed to pass all tests.
But I will hopefully be calling on some higher precision equipment for
the final alignment in due course.

I think one of the biggest lessons I've learned is not to over
compensate for my old soldering skills by minimizing solder too much.
Having got the right brand and gauge of solder, and an appropriate
temperature compensated iron, this heavy handed old vacuum tube builder
became just a little too frugal. Many joints needed an extra touch up
during testing, but hey, I'm learning!

The only thing i have noticed is that the audio gain does not seem to
act as I would expect while listening to an SSB signal - the volume
seems to increase marginally from minimum and then stay constant over
much of the range before increasing slightly at the end . Maybe this is
another case of an extra touch of solder somewhere, or maybe it's a
normal function of how the AGC level works?

Now, it's on to Assembly Part III, P67!!

73,
Kev VK5KS

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Don Wilhelm-4

Re: K2 Build #7552 Progress

Kevin,

The K2 alignment and calibration is designed to use the built-in tools
and they will allow you to align it to perfection.

There is one area that is missing from the manual information, and that
is the dial calibration and filter alignment. For that, take a look at
my webpage article dealing with Dial Calibration at www.w3fpr.com.
Ideally you should use Spectrogram for aligning the filters so you can
see the passband width and placement in the audio spectrum that is
produced by your filter width and BFO adjustments. You can download a
copy of Spectrogram from my website - look for the link near the bottom
of the opening page. This is a local copy that has been scanned for
'bad stuff' numerous times. Norton does not like it, but all other
scanners report it to be a good copy.

There are other good audio spectrum analyzers out there, but I happen to
like Spectrogram the best for this purpose.

73,
Don W3FPR

On 10/24/2014 9:27 PM, Kevin Schache wrote:

> I have now completed up to the start of Assembly, Part III, P67, with
> all tests and alignments done.
> AND BEST OF ALL, it works!! I have actually heard several strong SSB
> signals on 40M...... YAAYY!!
>
> Although I am limited with test equipment, I've managed to pass all
> tests.
> But I will hopefully be calling on some higher precision equipment for
> the final alignment in due course.
>
> I think one of the biggest lessons I've learned is not to over
> compensate for my old soldering skills by minimizing solder too much.
> Having got the right brand and gauge of solder, and an appropriate
> temperature compensated iron, this heavy handed old vacuum tube
> builder became just a little too frugal. Many joints needed an extra
> touch up during testing, but hey, I'm learning!
>
> The only thing i have noticed is that the audio gain does not seem to
> act as I would expect while listening to an SSB signal - the volume
> seems to increase marginally from minimum and then stay constant over
> much of the range before increasing slightly at the end . Maybe this
> is another case of an extra touch of solder somewhere, or maybe it's a
> normal function of how the AGC level works?
>
> Now, it's on to Assembly Part III, P67!!
>
> 73,
> Kev VK5KS
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

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Kev Schache

Re: K2 Build #7552 Progress

In reply to this post by Kev Schache

The four trimmers provided for C32, C34, C44, and C46 are supposed to be
5-30pF ceramics but the ones supplied appear to be quite different.

They have a brown plastic type body and don't appear to be ceramic. I
can find no markings on the trimmers to indicate their capacitance. The
inside adjustment screw head is + shaped rather than a single slot for
use with a small flat blade screwdriver. All this makes it difficult to
set these trimmers to the mid-point as specified in the manual page 68
Figure 6-23.
So I decide to find their midpoint by measuring them before inserting
them, but came up with 20 -70pF which is a lot different from the
expected 5-30pF.
I don't think my capacitance meter would be that far out.

The other two 50pF trimmers, C21 and C23 are certainly ceramic.
I've checked various assembly photos and they all appear to clearly show
ceramic trimmers.

Can anyone tell me if these are a correct replacement?
Should I proceed to find the measured midpoint of these on the basis
that they are a correct replacement?

Thanks,
Kev VK5KS

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Don Wilhelm-4

Re: K2 Build #7552 Progress

Kev,

Those are the trimmer caps that are currently used. Yes, they are not
ceramic, but they have good temperature compensation characteristics
(better than the original ceramics).

Observe the flat side orientation when installing those capacitors so
they can be properly adjusted when using a metallic adjustment tool. If
you cannot discern the flat side on the silkscreen, look at the parts
placement diagram in the back of the manual.

It is not essential that they be set to midpoint, you will be able to
easily determine the proper tuning point when you come to the alignment
procedure.

73,
Don W3FPR

On 10/26/2014 2:56 AM, Kevin Schache wrote:

> The four trimmers provided for C32, C34, C44, and C46 are supposed to
> be 5-30pF ceramics but the ones supplied appear to be quite different.
>
> They have a brown plastic type body and don't appear to be ceramic. I
> can find no markings on the trimmers to indicate their capacitance.
> The inside adjustment screw head is + shaped rather than a single slot
> for use with a small flat blade screwdriver. All this makes it
> difficult to set these trimmers to the mid-point as specified in the
> manual page 68 Figure 6-23.
> So I decide to find their midpoint by measuring them before inserting
> them, but came up with 20 -70pF which is a lot different from the
> expected 5-30pF.
> I don't think my capacitance meter would be that far out.
>
> The other two 50pF trimmers, C21 and C23 are certainly ceramic.
> I've checked various assembly photos and they all appear to clearly
> show ceramic trimmers.
>
> Can anyone tell me if these are a correct replacement?
> Should I proceed to find the measured midpoint of these on the basis
> that they are a correct replacement?
>
>
>
>
>
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>