[Elecraft] K2 BFO issues

[Don Wilhelm]

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 <donwilh at embarqmail.com>
> To: Anthony Clare <n3kcb at usa.net>, elecraft at mailman.qth.net
> 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.
>>
>
>