[Elecraft] K2 / KPA100 - net shorted on KPA100 --> C31 / D13 ... failure modes ?

[Don Wilhelm]

  Brian,

Why speculate, just remove C31 (it needs to be replaced anyway) and 
remeasure to confirm that C31 is indeed the problem - it quite likely is.

73,
Don W3FPR

On 1/22/2011 3:11 PM, OZ2BRN Brian Lodahl wrote:
> Hi there,
>
> After 100 % flawless work with the whole K2 journey, the KPA100 and all
> the add-on modules with bell's and whistles, it seems my turn has come
> now to have a build error on # 6936, or more specificly; the KPA-100:
>
> When doing the 2nd alignment step of KPA100, I measure all the
> resistances OK but one; The cathode of D13 seems very low resistance to
> ground and not>10 kohms as expected. I measured some 6-7 ohms.
>
> The intial checkout in 1st alignment step round confirmed all diodes
> pass and having the expected forward and reverse voltages / resistances
> as expected, so I assume for now the Diodes are OK still.
>
> Now I may have myself an idea to the failure mode, but can any of you
> think of other (known) failure modes to this ?
>
> My assumption is that I have shorted out the two foil layers of
> capacitor C31; effectively putting both sides of C31 to ground - as I
> managed to nick the house of C31 with my auxillary 30W solder iron, when
> soldering the emitters of Q1 and Q2, and the plastic housing of C31 is
> now slightly open and the internal foil visible.
>
> ( and yes; I'm givin' myself a hard time and cursing my own lack of
> being careful :-) !! )
>
> Any other bright ideas beyond the obvious C31 defect, hence replace ?
>
> 73'
> Brian OZ2BRN
>