[Elecraft] [K2} K2-100 Test and Alignment Issues

[Don Wilhelm]

As John has pointed out, the problem can be anywhere in the KPA100 
wattmeter circuit consisting of T4, C1, C95. R28, R29, D16, D17, R26, 
R27, U5. R24. R25, Q10, Q11, and U6.  With a bit more information and 
some measurements that I can suggest, the field of suspect components 
(and soldering thereof) can be reduced substantially.

73,
Don W3FPR

On 1/28/2014 3:31 PM, John Oglesby wrote:
> Bill - I had this exact problem on my K2/100 during testing.  Changing 
> C1 varied the power output, but the SWR was fixed at 9.9-1.  The 
> problem was a short between the output of the two op-amps U5A and U5B 
> that amplify and buffer the forward and reflected voltages before they 
> go to the processor.  There are two resistors on the outputs that are 
> very close to each other and the pads were shorted so the processor 
> saw the same voltage for forward and reflected - ergo SWR of 9.9-1. 
> And the voltage varied with the C1 setting as the bridge went in and 
> out of balance - ergo the varying power indication. Totally a build 
> error. When I folded over the resistor leads, they ended up looking 
> like they were on a single pad.  I think if you  look at that area you 
> will find the problem.
>