[Elecraft] [K2] K2 signal tracing progress and questions arising

[Don Wilhelm]

Paul,

Rather than trying to do your proposed test, I would suggest you look 
carefully at the T/R switch area first.  Typical problems are diodes 
oriented wrong (check against the Parts Placement diagram in the back of 
the manual).  A broken lead (or unsoldered, poorly tinned, etc.) of RFC3 
could cause similar problems  - be certain RFC3 is wound on a ferrite 
core (dark gray) and not one of the black cores.

73,
Don W3FPR

Paul Fletcher wrote:
>
> Don Wilhelm-4 wrote:
>   
>> A drop in signal at the receive output of the LPF could also be caused 
>> by a T/R switch problem.
>>
>>     
>
> Update so far. Having terminated the LPF's in a 50 ohm resistor I can
> definitely confirm all of the LPF's are fine. I measured swr and monitored
> in / out on the scope and loss is negligible. As soon as I reinstate W1 the
> output of the LPF is pulled low (50% of level when terminated with 50 ohms).
> I guess the next step is to do the same check with the chain broken after
> the T/R switch and progressively work down the chain. The is no ground short
> on the input to the band pass filters at DC. I can't directly terminate the
> T/R switch at W6 because of the DC bias so what value blocking cap should I
> use?
>
> Any other thoughts appreciated.
>
> 73 Paul M1PAF
>   
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