[Elecraft] [K2] K2 - No TX

[Don Wilhelm]

 From those measurements, you definitely had a problem between Q5 and 
Q6.  Congratulations on finding it.

The much higher than expected RF Voltages seems to mystify some builders 
- that is *not* a problem nor should it be cause for any alarm, but is 
normal behavior for the K2 power control circuits.  When there is no (or 
lower than requested) power output, the K2 increases the drive in an 
attempt to generate more power. 

The result is that the RF voltage in the *working* stages will increase 
above the normal (expected) value - when you progress just beyond the 
failing point, the RF Voltage will drop substantially below the expected 
value - that should tell you that you just passed the failure point.  It 
makes troubleshooting by transmit signal tracing a relatively easy task.

73,
Don W3FPR

djmd wrote:
> Just wanted to update anyone on here who might have been curious. I believe I
> found the intermittant. In the process of doing the tranmitter signal
> tracing I found that the problem appeared to be between the pre-driver
> output and the driver input. With the RF probe I was seeing 6v (!) on the
> case of Q5 (should have been less than a quarter vrms) and only about 3mv on
> the base of Q6. So I reheated and added a smidgen of solder to those
> components, as well as T1 and C121. It seems to work consistently now.
>
>
>
>
>
> djmd wrote:
>   
>> I'm going to do the transmit signal tracing tonight, but I'm starting to
>> think I may know the source of the problem.
>>     
>
>   
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