[Elecraft] K2 KSB2 low output

[gt-i at gmx.net]

Solved: PIC16C72A was defective.
I had the chance to get a second K2 for reference testing. The KSB2 of 
that K2 works perfectly in my K2, but not vice versa. The error is 
isolated to my KSB2, but now I'd need to seek for the culprit.
I noticed a strange behavior at U1.16, which drives the DAC-Converter 
for PWR-Level and ALC-THR. Yes, thats the PIC. I pulled out my old 
PICStart programmer, cloned the PIC of the working K2 and programmed a 
PIC16F876A which I had in the box. And here we go, full output power again!

73/72 Gernot DF5RF



Am 12.09.2017 um 22:59 schrieb gt-i at gmx.net:
> Hello again,
>
> Thanks to Volker, DL4ZBG, he replied directly with the following link: 
> http://www.qrpproject.de/Media/pdf/ZusammenfassungMods.pdf
> It is a nice description of many improvements that can be made for the 
> KSB2.
> However, I believe that I do have a fault in the KSB2 (Rev. D) or K2, 
> since I know it behaved differently years ago. For example, the ALC 
> shows 7 steady bars, no matter what power level I set nor how much SSB 
> amplitude is produced. Regardless of the power level set, the RF 
> signal is never stronger than 1 bar.
> I will try to experiment further, and I'm open to get any hints.
> Thanks!
>
> Gernot, DF5RF
>
>
> Am 12.09.2017 um 01:53 schrieb gt-i at gmx.net:
>> Hello list,
>> I recently tried to use my K2 on SSB. To my suprise, there was very 
>> little output. Even with full power it only showed the first bar. I 
>> did some SSB QSOs during the first years...
>> Digging deeper, I found the DSB signal showed a Vpp of ~1V, but after 
>> the filter the SSB signal was only 20mV or so. Is this kind of loss 
>> normal for a 7-pole filter? If not, any hints how to repair the filter?
>> tnx es 73
>> Gernot DF5RF
>>
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