[Elecraft] Its not over yet, I've gone back to basic K2 troubleshooting and find i have what seems a massive loss through the variable Crystal filter ?

[Clifford Hynds]

Ok Don,

T7 is right way round, continuity seems good

Audio does increase when AGC turned off

Unfortunately U12 output at pin 8 is much lower than pin4

with 0.14Vrms Ant input and RFgain at minimum

0.365Vrms at Pin4

0.025vRMS at Pin 8 changing to 0.151 when RF gain turned fully up.

U12 DC Voltages seem ok.

1    7.74
2    7.74
3   0
4   0
5  4
6   2.467
7   0
8   7.73

73
Cliff VK2CCJ



On Wed, Jan 30, 2013 at 1:27 PM, Don Wilhelm <w3fpr at embarqmail.com> wrote:

> Cliff,
>
> When looking at the RF voltage after the IF filter, tune the K2 slowly
> while looking for the peak RF voltage at U12 pin 4.
> You will not be able to see the IF amplifier saturation with diodes D40
> and D41 in place - that information is prior to the introduction of those
> diodes.
>
> T7 should be with the green winding closest to the crystal filter, the red
> winding adjacent to pins 4 and 5 of U12.
> Turn off the AGC (press PRE and REV buttons together) and see if the audio
> level comes up.
> You should have more RF voltage at U12 pin 8 than you do at U12 pin 4.
>
> 73,
> Don W3FPR
>
>
> On 1/29/2013 8:21 PM, Clifford Hynds wrote:
>
>> Still having issues with my K2,
>>
>> I did align the filters using the Spectrogram software so I believe they
>> are ok
>>
>> Well I decided to start from scratch and started RX troubleshooting/signal
>> tracing  before I go back to TX side want to make sure the RX is 100% and
>> while the stages up to the input of the crystal filter look ok the output
>> compared to the manual is extremely low.
>>
>> I ended up using the RF probe supplied in the kit so all is known.
>>
>> Also removed the SSB board and fitted the corresponding jumpers at W2 and
>> W3 and C167
>>
>> Here is what i am seeing with a 0.14Vrms input to the antenna  I used
>> 10.1Mhz but I tried other bands with similar results.
>>
>> All voltages up to the input of the variable crystal filter look normal.
>>
>> Case or collector of Q22 = 2.3Vrms
>>
>> At W2 = ~ 2Vrms
>>
>> cathode D30 =0.89Vrms
>>
>> cathode D31 =0.95Vrms
>>
>> cathode D32 =0.757Vrms
>>
>> cathode D33 =0.767Vrms
>>
>> cathode D34 =0.735Vrms
>>
>> W3 = 0.080Vrms  the K2 book on Page 11 says it should be about 0.34Vrms ,
>> I
>> am way low compared to that.
>>
>> I suspect either D34 or T7 ?
>>
>> Also I don't appear to be able to saturate IF amp it says I should read
>> approx 0.15Vrms at Pin 8 of U12
>>
>> Am I on the right track.
>>
>> Thanks again,
>> Cliff VK2CCJ
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