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[K2] Band-Pass Filter Trimcap values

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andrew-2

[K2] Band-Pass Filter Trimcap values

During initial build I didn't have a signal generator and wasn't happy with the band-pass filter alignment for the 12m and 17m bands which use trimcaps.
Revisiting the alignment with a newly acquired signal generator I found I couldn't get a correct adjustment and removed C46 - it's maximum value is 66pF when it should be approx 30pF.
I removed C32, C34 and C44 and all have a max of approx 66pF. I also checked C21 and C23 which are correct with a maximum of 50pF. (and different physical construction with Red mark)
Before I make replacements I would like to confirm that the correct values should be:

C21, C23 = max 50pF
C32, C34, C44, C46 = max 30pF

Many thanks
Andrew
VK6WAX
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Don Wilhelm-4

Re: [K2] Band-Pass Filter Trimcap values

Andrew,

C21 and C23 are good with the ceramic capacitors with the red dot - use
those supplied with your kit.
C32 and C34 need approximately 25 pF to tune, and your current brown
trimmers should do the job nicely.
For C44 and C46 the capacity needed is approximately 10 pF (the brown
body trimmers will *not* work).
The trimmers currently being supplied for use at C44 and C46 are PN
E540011 and have a red body.

If you ordered your K2 in the last quarter of 2014 the kit was supplied
with 4 brown bodied trimmer capacitors (that was corrected in
December), which were supposed to have a minimum capacity of 6pF but
the actual minimum capacity is more like 20pF. I don't know if the
manufacturer had an incorrect value on the data sheet, or what happened,
but the actual range of those brown trimmers is nominally 20 to 60pF.

So bottom line, the brown trimmers will work fine at C32 and C34 and are
what is currently being supplied in new kits.
The trimmers now being used for C44 and C46 are PN E540011 and have a
red body. You can request those from parts (at) elecraft.com.

If you want to procure trimmers locally, and you can fine 5-30pF
trimmers, they will work, but watch the minimum capacitance of anything
you substitute, particularly for C44 and C46.

73,
Don W3FPR

On 10/2/2015 6:04 AM, andrew wrote:
> During initial build I didn't have a signal generator and wasn't happy with the band-pass filter alignment for the 12m and 17m bands which use trimcaps.
> Revisiting the alignment with a newly acquired signal generator I found I couldn't get a correct adjustment and removed C46 - it's maximum value is 66pF when it should be approx 30pF.
> I removed C32, C34 and C44 and all have a max of approx 66pF. I also checked C21 and C23 which are correct with a maximum of 50pF. (and different physical construction with Red mark)
> Before I make replacements I would like to confirm that the correct values should be:
>
> C21, C23 = max 50pF
> C32, C34, C44, C46 = max 30pF
>
>

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Edward A. Dauer

[K2] Band-Pass Filter Trimcap values

In reply to this post by andrew-2

Don —

I have just had a back-and-forth with Elecraft Parts about the same
question.

The K2 Manual, dated March 2012, lists for C44, C46, C32, and C34 trimmers
p/n E540001, 5-30pF. However, Revision I-3 dated September 1, 2015, lists
for C32 and C34 p/n E540002, 10-50 pF; and for C44 and C46, p/n E540001,
5-30 pF. What I received in a kit ordered on Sept. 7 was apparently what
the I-3 Revision called for - there were two white ceramic and two bright
red plastic trimmers, with no markings on either to say which was which.
When I inquired, Parts told me (two days ago) that the red plastic
trimmers were p/n E540001, and that (here’s the quote), "we'll send the 4
E540002 trimmers. The E540001 trimmers are obsolete and you can use the
E540002 trimmers in place of them.”

Taking this together with your note leaves me wondering . . . Help?

As an aside, the C21 and C23 values are listed in both the Manual and the
Revision as p/n 540000, 8-50 pF.

Ted, KN1CBR

>Message: 29
>Date: Fri, 2 Oct 2015 08:28:07 -0400
>From: Don Wilhelm <[hidden email]>
>To: andrew <[hidden email]>, [hidden email]
>Subject: Re: [Elecraft] [K2] Band-Pass Filter Trimcap values
>Message-ID: <[hidden email]>
>Content-Type: text/plain; charset=windows-1252; format=flowed
>
>Andrew,
>
>C21 and C23 are good with the ceramic capacitors with the red dot - use
>those supplied with your kit.
>C32 and C34 need approximately 25 pF to tune, and your current brown
>trimmers should do the job nicely.
>For C44 and C46 the capacity needed is approximately 10 pF (the brown
>body trimmers will *not* work).
>The trimmers currently being supplied for use at C44 and C46 are PN
>E540011 and have a red body.
>
>If you ordered your K2 in the last quarter of 2014 the kit was supplied
>with 4 brown bodied trimmer capacitors (that was corrected in
>December), which were supposed to have a minimum capacity of 6pF but
>the actual minimum capacity is more like 20pF. I don't know if the
>manufacturer had an incorrect value on the data sheet, or what happened,
>but the actual range of those brown trimmers is nominally 20 to 60pF.
>
>So bottom line, the brown trimmers will work fine at C32 and C34 and are
>what is currently being supplied in new kits.
>The trimmers now being used for C44 and C46 are PN E540011 and have a
>red body. You can request those from parts (at) elecraft.com.
>
>If you want to procure trimmers locally, and you can fine 5-30pF
>trimmers, they will work, but watch the minimum capacitance of anything
>you substitute, particularly for C44 and C46.
>
>73,
>Don W3FPR
>
>
>On 10/2/2015 6:04 AM, andrew wrote:
>> During initial build I didn't have a signal generator and wasn't happy
>>with the band-pass filter alignment for the 12m and 17m bands which use
>>trimcaps.
>> Revisiting the alignment with a newly acquired signal generator I found
>>I couldn't get a correct adjustment and removed C46 - it's maximum value
>>is 66pF when it should be approx 30pF.
>> I removed C32, C34 and C44 and all have a max of approx 66pF. I also
>>checked C21 and C23 which are correct with a maximum of 50pF. (and
>>different physical construction with Red mark)
>> Before I make replacements I would like to confirm that the correct
>>values should be:
>>
>> C21, C23 = max 50pF
>> C32, C34, C44, C46 = max 30pF
>>
>****************************************

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andrew-2

Re: [K2] Band-Pass Filter Trimcap values

In reply to this post by Don Wilhelm-4

Hello Don
Thanks very much for the useful information.
I was able to source some trimcaps with the correct pin-spacing and a nominal range of 3 - 30pF.
The maximum values used bacame:
C21, C23, C32, C34 = 50pF
C44, C46 = 30pF
These resulted in all bands being easily tuned for peak output close to the middle of the trimming adjustment.
Thanks again.
Andrew
vk6wax

---- Don Wilhelm <[hidden email]> wrote:

> Andrew,
>
> C21 and C23 are good with the ceramic capacitors with the red dot - use
> those supplied with your kit.
> C32 and C34 need approximately 25 pF to tune, and your current brown
> trimmers should do the job nicely.
> For C44 and C46 the capacity needed is approximately 10 pF (the brown
> body trimmers will *not* work).
> The trimmers currently being supplied for use at C44 and C46 are PN
> E540011 and have a red body.
>
> If you ordered your K2 in the last quarter of 2014 the kit was supplied
> with 4 brown bodied trimmer capacitors (that was corrected in
> December), which were supposed to have a minimum capacity of 6pF but
> the actual minimum capacity is more like 20pF. I don't know if the
> manufacturer had an incorrect value on the data sheet, or what happened,
> but the actual range of those brown trimmers is nominally 20 to 60pF.
>
> So bottom line, the brown trimmers will work fine at C32 and C34 and are
> what is currently being supplied in new kits.
> The trimmers now being used for C44 and C46 are PN E540011 and have a
> red body. You can request those from parts (at) elecraft.com.
>
> If you want to procure trimmers locally, and you can fine 5-30pF
> trimmers, they will work, but watch the minimum capacitance of anything
> you substitute, particularly for C44 and C46.
>
> 73,
> Don W3FPR
>
>
> On 10/2/2015 6:04 AM, andrew wrote:
> > During initial build I didn't have a signal generator and wasn't happy with the band-pass filter alignment for the 12m and 17m bands which use trimcaps.
> > Revisiting the alignment with a newly acquired signal generator I found I couldn't get a correct adjustment and removed C46 - it's maximum value is 66pF when it should be approx 30pF.
> > I removed C32, C34 and C44 and all have a max of approx 66pF. I also checked C21 and C23 which are correct with a maximum of 50pF. (and different physical construction with Red mark)
> > Before I make replacements I would like to confirm that the correct values should be:
> >
> > C21, C23 = max 50pF
> > C32, C34, C44, C46 = max 30pF
> >
> >
>

andrew-2

Re: [K2] Band-Pass Filter Trimcap values

Hello Ted

From your callsign I'm assuming your are in the USA, in which case I would recommend sourcing any required parts direct from Elecraft. I'm in VK-land so it was expedient to source locally.

The values I had success with are noted below, which tallies with the advice from Don and the updated errata I-3.

Best wishes with your K2 build.
Andrew
vk6wax

---- "Dauer wrote:
> Andrew —
>
> What is the source? I am still wrestling with this problem.
>
> Tnx,
>
> Ted, KN1CBR

---- andrew <[hidden email]> wrote:

> Hello Don
> Thanks very much for the useful information.
> I was able to source some trimcaps with the correct pin-spacing and a nominal range of 3 - 30pF.
> The maximum values used bacame:
> C21, C23, C32, C34 = 50pF
> C44, C46 = 30pF
> These resulted in all bands being easily tuned for peak output close to the middle of the trimming adjustment.
> Thanks again.
> Andrew
> vk6wax
>
> ---- Don Wilhelm <[hidden email]> wrote:
> > Andrew,
> >
> > C21 and C23 are good with the ceramic capacitors with the red dot - use
> > those supplied with your kit.
> > C32 and C34 need approximately 25 pF to tune, and your current brown
> > trimmers should do the job nicely.
> > For C44 and C46 the capacity needed is approximately 10 pF (the brown
> > body trimmers will *not* work).
> > The trimmers currently being supplied for use at C44 and C46 are PN
> > E540011 and have a red body.
> >
> > If you ordered your K2 in the last quarter of 2014 the kit was supplied
> > with 4 brown bodied trimmer capacitors (that was corrected in
> > December), which were supposed to have a minimum capacity of 6pF but
> > the actual minimum capacity is more like 20pF. I don't know if the
> > manufacturer had an incorrect value on the data sheet, or what happened,
> > but the actual range of those brown trimmers is nominally 20 to 60pF.
> >
> > So bottom line, the brown trimmers will work fine at C32 and C34 and are
> > what is currently being supplied in new kits.
> > The trimmers now being used for C44 and C46 are PN E540011 and have a
> > red body. You can request those from parts (at) elecraft.com.
> >
> > If you want to procure trimmers locally, and you can fine 5-30pF
> > trimmers, they will work, but watch the minimum capacitance of anything
> > you substitute, particularly for C44 and C46.
> >
> > 73,
> > Don W3FPR
> >
> >
> > On 10/2/2015 6:04 AM, andrew wrote:
> > > During initial build I didn't have a signal generator and wasn't happy with the band-pass filter alignment for the 12m and 17m bands which use trimcaps.
> > > Revisiting the alignment with a newly acquired signal generator I found I couldn't get a correct adjustment and removed C46 - it's maximum value is 66pF when it should be approx 30pF.
> > > I removed C32, C34 and C44 and all have a max of approx 66pF. I also checked C21 and C23 which are correct with a maximum of 50pF. (and different physical construction with Red mark)
> > > Before I make replacements I would like to confirm that the correct values should be:
> > >
> > > C21, C23 = max 50pF
> > > C32, C34, C44, C46 = max 30pF
> > >
> > >
> >