[Elecraft] Help - K2 Higher Noise Level with X1 Selected

[VK1OO]

Hi Don,

As usual, thanks for your assistance.   Pulling seven crystals with no 
super confidence that that's the problem seems hard work.  How often 
does a crystal die?  I've not had that fault before in any of my equipment.

I have an XG3 sig gen (known level) and access to a CRO.  Is there any 
level testing comparison I can do to get a sense of where the problem is?
Is there a matrix describing switching paths with their inputs and 
outputs?  If not, could you describe the area of the circuit I need to 
look at and understand. Seems like I need some way of stepping through 
the combinations and confirming they work / finding what doesn't.

Cheers
Mike

On 25-Jun-12 6:20 AM, Don Wilhelm wrote:
> Mike,
>
> I can see that, but unfortunately, it does not help with the isolation 
> of the problem.
> Ome easy thing you could do is assume a bad crystal in the set on the 
> base K2 board and try replacing the 7 crystals.  If I were to make a 
> first guess, that would be what I would do.
>
> OTOH, there may be a problem with the switching path through the KSB2 
> diodes that change the path for the two filters.  Since you have 
> already checked the diodes for orientation, that is not as likely as a 
> faulty crystal.
>
> 73,
> Don W3FPR
>
> On 6/23/2012 3:09 AM, VK1OO wrote:
>> Hi Don,
>>
>> I've attached a ppt showing FL1-FL4 (Slide 1-Slide 4) responses to 
>> broadband noise. I could send separate jpg if necessary.
>>
>> You can see the reduction in signal (audio) between FL1, and FL2-4.
>> FL1 sounds louder and has the extra three S Meter bars.
>>
>> Mike
>>
>>
>>
>> On 17-Jun-12 10:19 PM, Don Wilhelm wrote:
>>> Mike,
>>>
>>>
>>>
>>>
>>>
>>> OK, back up a step and look at the amplitude of the passband when 
>>> using Spectrogram.
>>> The OP1 filter and the other filters should have close to the same 
>>> amplitude when the K2 is fed with a broadband noise generator.
>>>
>>> Please verify for that condition.
>>>
>>> 73,
>>> Don W3FPR
>>>
>>> On 6/17/2012 7:04 AM, VK1OO wrote:
>>>> Don,
>>>>
>>>> Still no joy with this problem.  I've resoldered most of the joints on
>>>> the KSB2, checked the torroids etc  and have gone back and checked the
>>>> filters with a noise generator and spectrogram.
>>>> What feature of the circuit would account for the increase in S 
>>>> meter bars?
>>>>
>>>> Mike
>>>> VK1OO
>>>>
>>>>
>>>> On 10-Jun-12 10:12 AM, Don Wilhelm wrote:
>>>>> Mike,
>>>>>
>>>>> Two different filters - the FL1 OP1 filter is the one on the KSB2
>>>>> board while the others are created from the variable bandwidth filter
>>>>> on the RF board.  Since all but OP1 work correctly, it has to be the
>>>>> OP1 filter on the KSB2 board.
>>>>>
>>>>> Oh, one more piece of info - when you remove the KSB2 board, the OP1
>>>>> filter goes away, and the filtering defaults to a 2.20 bandwidth
>>>>> filter from the filter on the RF Board.
>>>>>
>>>>> 73,
>>>>> Don W3FPR
>>>>>
>>>>> On 6/9/2012 7:54 PM, VK1OO wrote:
>>>>>> Hi Don,
>>>>>>
>>>>>> Wow, thanks for fast response noting it must be late there.
>>>>>>
>>>>>> I will do.  What conclusion can be drawn from X1 being affected, and
>>>>>> not X2-4?
>>>>>>
>>>>>> Mike
>>>>>> VK1OO
>>>>>>
>>>>>> On 10-Jun-12 9:43 AM, Don Wilhelm wrote:
>>>>>>> Mike,
>>>>>>>
>>>>>>> It is on the KSB2 board somewhere.  Check everything on the end of
>>>>>>> that board containing the filter crystals.  Check T1 and T2 to be
>>>>>>> certain all the leads are well stripped,  tinned and soldered 
>>>>>>> and be
>>>>>>> sure there are no shorted turns on those toroids.  I recently
>>>>>>> repaired a K2 that had the shorted turn problem because the builder
>>>>>>> use a flame to burn off the insulation from the toroid wires and 
>>>>>>> got
>>>>>>> too much flame on the red T2 wires when he tried to strip the green
>>>>>>> leads.
>>>>>>>
>>>>>>> 73,
>>>>>>> Don W3FPR
>>>>>>>
>>>>>>> On 6/9/2012 7:29 PM, VK1OO wrote:
>>>>>>>> Hi Don,
>>>>>>>>
>>>>>>>> We have a long weekend here, so I've been able to get back to 
>>>>>>>> this.
>>>>>>>> I reflowed RF board and KSB2 board, with no improvement.
>>>>>>>>
>>>>>>>> I then took out the KSB2, inserting the previously removed links
>>>>>>>> and the capacitor (effectively returning radio to pre-KSB2 state).
>>>>>>>> The noise problem on X1 goes away.
>>>>>>>>
>>>>>>>> Your thoughts on what to look at next would be appreciated.
>>>>>>>>
>>>>>>>> Mike
>>>>>>>> VK1OO
>>>>>>>>
>>>>>>>>
>>>>>>>> On 03-Jun-12 6:59 AM, Don Wilhelm wrote:
>>>>>>>>> Mike,
>>>>>>>>>
>>>>>>>>> If you do not find the solution re-flowing the solder on the RF
>>>>>>>>> board filter area, the problem source may be on the KSB2 board in
>>>>>>>>> the switching diodes and/or resistors at the filter end of that
>>>>>>>>> board, so for completeness, reflow those connections as well.
>>>>>>>>>
>>>>>>>>> 73,
>>>>>>>>> Don W3FPR
>>>>>>>>>
>>>>>>>>> On 6/2/2012 4:24 PM, VK1OO wrote:
>>>>>>>>>> Don,
>>>>>>>>>>
>>>>>>>>>> The effect happens when the antenna is disconnected as well 
>>>>>>>>>> as when
>>>>>>>>>> connected.
>>>>>>>>>> And in SBB and CW
>>>>>>>>>>
>>>>>>>>>> SSB Filter Widths
>>>>>>>>>> X1 = OP1
>>>>>>>>>> X2 = 2.4
>>>>>>>>>> X3 = 2.1
>>>>>>>>>> X4 = 1.8
>>>>>>>>>>
>>>>>>>>>> CW Filter Widths
>>>>>>>>>> X1 = OP1
>>>>>>>>>> X2 = 0.7
>>>>>>>>>> X3 = 0.4
>>>>>>>>>> X4 = 0.1
>>>>>>>>>>
>>>>>>>>>> I assume something is going wrong in the 4.915MHz Variable 
>>>>>>>>>> Bandwidth
>>>>>>>>>> Crystal Filter.
>>>>>>>>>>
>>>>>>>>>>
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>>>
>>>
>>>
>
>
>