[Elecraft] K2 Q7 unstable resistance

[R. Kevin Stover]

MikeH wrote:
> Hello Group,
> 
> The build for K2 #4661 continues...
> 
> I am doing the final resistance check on p. 71 of the K2 manual (the RF 
> board is basically complete now), and I am getting unstable readings on 
> the Q7 collector. The readings are all above 500 ohms, as they should 
> be, but they are constantly changing. Hopefully this is normal? I get 
> the same sort of response on the Q8 collector (although it's not one of 
> the resistance checks). All other readings are ok.

Hi Mike.

My K2, #4684 does the same thing and believe it caused by a cap charging 
from DMM current. As long as you don't show a short you should be OK. 
When you get to the next step of mounting the finals to the heatsink 
double and triple check to make sure the tabs of the transistors are 
flat and parallel to the heat sink and are slightly above the 2D 
connector between them.

For me, the best way to make sure the thermal pads are installed 
correctly and will stay in place while installing the heatsink is to 
take the wide flat edge of the green alignment tool and gently "smooth" 
the pads down onto the transistors. Slight pressure only as you don't 
want to rip the pads.

Once you've got the heatsink installed recheck the resistance on both Q7 
and Q8 collectors to make sure you don't have a short.

Good luck.



-- 
R. Kevin Stover	ACØH

K2/100 #4684

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