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K2 BFO issues

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Anthony Clare

K2 BFO issues

Hello:

Looks like I am not the only one to have this problem. Just finished assembly
phase 2(?) on the K2. It was during the BFO tests that I realized there was
not enough signal at the test point for the internal counter. I checked for
poor solder, improper varactor diode install, verified that L33 was intact and
not being shorted by the 5 meg resistor, etc. I ran one crystal at a time, but
neither one would provide the proper signal level alone. I even checked L33 on
the inductance meter and it came out to about 39uH, which seems about right. I
assume the inductance meter has some error. The resistor measures out to about
5 meg.

Anyway, with the test pojnt NOT active, I get about 385 mV at pin 6 of the
NE602. in counter mode, that drops into the 250 mV range and I get about 25 mV
at the test point. When i use the band up/down buttons to check BFO range, it
drops to around 10 mV at either end.

I even tried some other crystals (4.915, 5.242, 9.000, etc.) I had laying
around to see what happened. Same low signal levels.

I hate to shotgun, but I have already replaced the 602 and J-310 since I have
tons in the parts pins.

Any ideas?

Anthony
n3kcb

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Don Wilhelm

Re: K2 BFO issues

Anthony,

When you put the K2 into CAL FCTR mode, what is the voltage at the ends
of R98 (on the bottom of the board). I am interested only in the
highest voltage.

With the new K2s (those using the new encoder board), many strange
problems are caused by contact of the encoder board with the Control Board.
You must flush trim the leads on the encoder board - and I mean almost
right down to the board level.
Also you must flush trim the back of the Control Board in the area that
could come in contact with the encoder board.
Make sure the rubber bumper pads are in place at the top corners of the
Front Panel Board.

As a test, remove the 2 screws that secure the Control Board to the
Front Panel and tilt the top of the Control Board to the rear. If
things then behave normally, you can be certain that contact between the
encoder board and the Control Board is causing the problem.

73,
Don W3FPR

On 5/30/2017 8:07 AM, Anthony Clare wrote:

> Hello:
>
> Looks like I am not the only one to have this problem. Just finished assembly
> phase 2(?) on the K2. It was during the BFO tests that I realized there was
> not enough signal at the test point for the internal counter. I checked for
> poor solder, improper varactor diode install, verified that L33 was intact and
> not being shorted by the 5 meg resistor, etc. I ran one crystal at a time, but
> neither one would provide the proper signal level alone. I even checked L33 on
> the inductance meter and it came out to about 39uH, which seems about right. I
> assume the inductance meter has some error. The resistor measures out to about
> 5 meg.
>

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Anthony Clare

Re: K2 BFO issues

In reply to this post by Anthony Clare

Hello:

I am not at home to try, so I will have to check R98 later. I remember fitting
the encoder and it was definitely a tight fit. I used a dremel sanding drum to
almost completely flatten the pins in the affected area on the encoder board
and control board. Then I reflowed all the connections that I flattened and
placed fiberglass tape over the encoder board. Once I did this, I could look
between the boards and see no physical contact.

I will separate the control and front panel boards and see what happens when I
get home.

Thanks,
Anthony
n3kcb

------ Original Message ------
Received: Tue, 30 May 2017 08:51:03 AM EDT
From: Don Wilhelm <[hidden email]>
To: Anthony Clare <[hidden email]>, [hidden email]
Subject: Re: [Elecraft] K2 BFO issues

Anthony,

When you put the K2 into CAL FCTR mode, what is the voltage at the ends
of R98 (on the bottom of the board). I am interested only in the
highest voltage.

With the new K2s (those using the new encoder board), many strange
problems are caused by contact of the encoder board with the Control Board.
You must flush trim the leads on the encoder board - and I mean almost
right down to the board level.
Also you must flush trim the back of the Control Board in the area that
could come in contact with the encoder board.
Make sure the rubber bumper pads are in place at the top corners of the
Front Panel Board.

As a test, remove the 2 screws that secure the Control Board to the
Front Panel and tilt the top of the Control Board to the rear. If
things then behave normally, you can be certain that contact between the
encoder board and the Control Board is causing the problem.

73,
Don W3FPR

On 5/30/2017 8:07 AM, Anthony Clare wrote:
> Hello:
>
> Looks like I am not the only one to have this problem. Just finished
assembly
> phase 2(?) on the K2. It was during the BFO tests that I realized there was
> not enough signal at the test point for the internal counter. I checked for
> poor solder, improper varactor diode install, verified that L33 was intact
and
> not being shorted by the 5 meg resistor, etc. I ran one crystal at a time,
but
> neither one would provide the proper signal level alone. I even checked L33
on
> the inductance meter and it came out to about 39uH, which seems about right.
I
> assume the inductance meter has some error. The resistor measures out to
about
> 5 meg.
>

______________________________________________________________
Elecraft mailing list
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
Message delivered to [hidden email]

Don Wilhelm

Re: K2 BFO issues

Anthony,

If you do not find more than 7 volts at the end of R98 that is furthest
away from Q24, then look at the U10A/Q8 circuit on the Control Board.
Check the associated components and their soldering. That is more
likely to be the problem than the active devices.

73,
Don W3FPR

On 5/30/2017 9:28 AM, Anthony Clare wrote:

> Hello:
>
> I am not at home to try, so I will have to check R98 later. I remember fitting
> the encoder and it was definitely a tight fit. I used a dremel sanding drum to
> almost completely flatten the pins in the affected area on the encoder board
> and control board. Then I reflowed all the connections that I flattened and
> placed fiberglass tape over the encoder board. Once I did this, I could look
> between the boards and see no physical contact.
>
> I will separate the control and front panel boards and see what happens when I
> get home.
>
> Thanks,
> Anthony
> n3kcb
>
> ------ Original Message ------
> Received: Tue, 30 May 2017 08:51:03 AM EDT
> From: Don Wilhelm <[hidden email]>
> To: Anthony Clare <[hidden email]>, [hidden email]
> Subject: Re: [Elecraft] K2 BFO issues
>
> Anthony,
>
> When you put the K2 into CAL FCTR mode, what is the voltage at the ends
> of R98 (on the bottom of the board). I am interested only in the
> highest voltage.
>
> With the new K2s (those using the new encoder board), many strange
> problems are caused by contact of the encoder board with the Control Board.
> You must flush trim the leads on the encoder board - and I mean almost
> right down to the board level.
> Also you must flush trim the back of the Control Board in the area that
> could come in contact with the encoder board.
> Make sure the rubber bumper pads are in place at the top corners of the
> Front Panel Board.
>
> As a test, remove the 2 screws that secure the Control Board to the
> Front Panel and tilt the top of the Control Board to the rear. If
> things then behave normally, you can be certain that contact between the
> encoder board and the Control Board is causing the problem.
>
> 73,
> Don W3FPR
>
> On 5/30/2017 8:07 AM, Anthony Clare wrote:
>> Hello:
>>
>> Looks like I am not the only one to have this problem. Just finished
> assembly
>> phase 2(?) on the K2. It was during the BFO tests that I realized there was
>> not enough signal at the test point for the internal counter. I checked for
>> poor solder, improper varactor diode install, verified that L33 was intact
> and
>> not being shorted by the 5 meg resistor, etc. I ran one crystal at a time,
> but
>> neither one would provide the proper signal level alone. I even checked L33
> on
>> the inductance meter and it came out to about 39uH, which seems about right.
> I
>> assume the inductance meter has some error. The resistor measures out to
> about
>> 5 meg.
>>
>
>

Anthony Clare

Re: K2 BFO issues

In reply to this post by Anthony Clare

Don:

I just looked at the schematic. I do remember checking the voltage at R98 now
that I look at it. I do recall getting over 7 volts in and somewhere around
5.8 give or take at the drain of Q24.

I never thought to look at U10 or associated circuitry. I will do that as soon
as I get home.

Thanks,
Anthony
n3kcb

------ Original Message ------
Received: Tue, 30 May 2017 10:14:48 AM EDT
From: Don Wilhelm <[hidden email]>
To: Anthony Clare <[hidden email]>, [hidden email]
Subject: Re: [Elecraft] K2 BFO issues

Anthony,

If you do not find more than 7 volts at the end of R98 that is furthest
away from Q24, then look at the U10A/Q8 circuit on the Control Board.
Check the associated components and their soldering. That is more
likely to be the problem than the active devices.

73,
Don W3FPR

On 5/30/2017 9:28 AM, Anthony Clare wrote:
> Hello:
>
> I am not at home to try, so I will have to check R98 later. I remember
fitting
> the encoder and it was definitely a tight fit. I used a dremel sanding drum
to
> almost completely flatten the pins in the affected area on the encoder
board
> and control board. Then I reflowed all the connections that I flattened and
> placed fiberglass tape over the encoder board. Once I did this, I could
look
> between the boards and see no physical contact.
>
> I will separate the control and front panel boards and see what happens when
I

> get home.
>
> Thanks,
> Anthony
> n3kcb
>
> ------ Original Message ------
> Received: Tue, 30 May 2017 08:51:03 AM EDT
> From: Don Wilhelm <[hidden email]>
> To: Anthony Clare <[hidden email]>, [hidden email]
> Subject: Re: [Elecraft] K2 BFO issues
>
> Anthony,
>
> When you put the K2 into CAL FCTR mode, what is the voltage at the ends
> of R98 (on the bottom of the board). I am interested only in the
> highest voltage.
>
> With the new K2s (those using the new encoder board), many strange
> problems are caused by contact of the encoder board with the Control Board.
> You must flush trim the leads on the encoder board - and I mean almost
> right down to the board level.
> Also you must flush trim the back of the Control Board in the area that
> could come in contact with the encoder board.
> Make sure the rubber bumper pads are in place at the top corners of the
> Front Panel Board.
>
> As a test, remove the 2 screws that secure the Control Board to the
> Front Panel and tilt the top of the Control Board to the rear. If
> things then behave normally, you can be certain that contact between the
> encoder board and the Control Board is causing the problem.
>
> 73,
> Don W3FPR
>
> On 5/30/2017 8:07 AM, Anthony Clare wrote:
>> Hello:
>>
>> Looks like I am not the only one to have this problem. Just finished
> assembly
>> phase 2(?) on the K2. It was during the BFO tests that I realized there

was
>> not enough signal at the test point for the internal counter. I checked
for
>> poor solder, improper varactor diode install, verified that L33 was intact
> and
>> not being shorted by the 5 meg resistor, etc. I ran one crystal at a time,
> but
>> neither one would provide the proper signal level alone. I even checked
L33
> on
>> the inductance meter and it came out to about 39uH, which seems about
right.
> I
>> assume the inductance meter has some error. The resistor measures out to
> about
>> 5 meg.
>>
>
>

______________________________________________________________
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]

Don Wilhelm

Re: K2 BFO issues

Anthony,

If you are getting 7 volts onto R98, there is no need to look into the
U10 circuits.
Check the values and soldering in other parts of the RF Board BFO and
Q24 area.
Is D36 installed properly using pins 2 and 3 on the SMT board with the
#2 lead in the hole of the silkscreen with the banded end?

73,
Don W3FPR

On 5/30/2017 11:26 AM, Anthony Clare wrote:

> Don:
>
> I just looked at the schematic. I do remember checking the voltage at R98 now
> that I look at it. I do recall getting over 7 volts in and somewhere around
> 5.8 give or take at the drain of Q24.
>
> I never thought to look at U10 or associated circuitry. I will do that as soon
> as I get home.
>
> Thanks,
> Anthony
> n3kcb
>
> ------ Original Message ------
> Received: Tue, 30 May 2017 10:14:48 AM EDT
> From: Don Wilhelm <[hidden email]>
> To: Anthony Clare <[hidden email]>, [hidden email]
> Subject: Re: [Elecraft] K2 BFO issues
>
> Anthony,
>
> If you do not find more than 7 volts at the end of R98 that is furthest
> away from Q24, then look at the U10A/Q8 circuit on the Control Board.
> Check the associated components and their soldering. That is more
> likely to be the problem than the active devices.
>
> 73,
> Don W3FPR
>
> On 5/30/2017 9:28 AM, Anthony Clare wrote:
>> Hello:
>>
>> I am not at home to try, so I will have to check R98 later. I remember
> fitting
>> the encoder and it was definitely a tight fit. I used a dremel sanding drum
> to
>> almost completely flatten the pins in the affected area on the encoder
> board
>> and control board. Then I reflowed all the connections that I flattened and
>> placed fiberglass tape over the encoder board. Once I did this, I could
> look
>> between the boards and see no physical contact.
>>
>> I will separate the control and front panel boards and see what happens when
> I
>> get home.
>>
>> Thanks,
>> Anthony
>> n3kcb
>>
>> ------ Original Message ------
>> Received: Tue, 30 May 2017 08:51:03 AM EDT
>> From: Don Wilhelm <[hidden email]>
>> To: Anthony Clare <[hidden email]>, [hidden email]
>> Subject: Re: [Elecraft] K2 BFO issues
>>
>> Anthony,
>>
>> When you put the K2 into CAL FCTR mode, what is the voltage at the ends
>> of R98 (on the bottom of the board). I am interested only in the
>> highest voltage.
>>
>> With the new K2s (those using the new encoder board), many strange
>> problems are caused by contact of the encoder board with the Control Board.
>> You must flush trim the leads on the encoder board - and I mean almost
>> right down to the board level.
>> Also you must flush trim the back of the Control Board in the area that
>> could come in contact with the encoder board.
>> Make sure the rubber bumper pads are in place at the top corners of the
>> Front Panel Board.
>>
>> As a test, remove the 2 screws that secure the Control Board to the
>> Front Panel and tilt the top of the Control Board to the rear. If
>> things then behave normally, you can be certain that contact between the
>> encoder board and the Control Board is causing the problem.
>>
>> 73,
>> Don W3FPR
>>
>> On 5/30/2017 8:07 AM, Anthony Clare wrote:
>>> Hello:
>>>
>>> Looks like I am not the only one to have this problem. Just finished
>> assembly
>>> phase 2(?) on the K2. It was during the BFO tests that I realized there
> was
>>> not enough signal at the test point for the internal counter. I checked
> for
>>> poor solder, improper varactor diode install, verified that L33 was intact
>> and
>>> not being shorted by the 5 meg resistor, etc. I ran one crystal at a time,
>> but
>>> neither one would provide the proper signal level alone. I even checked
> L33
>> on
>>> the inductance meter and it came out to about 39uH, which seems about
> right.
>> I
>>> assume the inductance meter has some error. The resistor measures out to
>> about
>>> 5 meg.
>>>
>>
>
>
>