[Elecraft] K2-Control Board Resistance Test

[Don Wilhelm]

Phil,

The most likely problem is that you have a solder bridge somewhere (or 
perhaps several).  Look at the amount of solder on your connections.  If 
it has more than a very small fillet, there is too much solder.  
Actually with the plated through holes just enough solder to fill the 
holes is sufficient, but I like to see a small fillet on the solder pad.

The solder connections should *not* look like 'balls of solder' (with a 
convex shape), the solder joints should have a concave shape to them.  
It has been said that a good solder joint looks like a mountain, but not 
a volcano.  Connections that have a concave shape usually indicate that 
insufficient heat was applied to the solder pad, and the solder did not 
flow out sufficiently.

If you do have too much solder, the cure is to take some away - solder 
wick works nicely or a professional type de-soldering tool works more 
quickly.  I know it is a lot of work to wick away the excess solder, but 
if I have described the condition of your Control Board correctly, that 
is the only positive cure.  In the future, heat the solder connection 
fully so the solder flows out well and control the amount of solder - 
this is *not* a thing where 'more is better'.  A small diameter solder 
allows better control of the amount applied.

73,
Don W3FPR

Philip L. Graitcer wrote:
> First time kit builder and have just completed control board, but  
> resistance checks do not seem to check out for several points:
>
> P2, U5, U4 are all okay
> *Q1 & Q2 collectors - both around 29K
> U6 - pin 8 is okay (about 75K),
> *U6 - pins 13, 14, are around 40K,
> U6 - pins 29 and 30 are okay (around 40K)
> *U8 - pin 2 about 40.7K, pins 15, 16, both 29.3K
>
> I have inspected all solder joints with magnifier. I double checked  
> components.
>
> What should I do next?
>
> Phil, W3HZZ
>   
>