[Elecraft] SWR Bridge Null Adjustment Problem: Can not null reflected voltage

[JimWMiller@aol.com]

Good Evening,
Ive just completed assembling the the 100 watt PA and ran into a problem with 
the SWR Null adjustment.  I'm at the point (page 44) where the K2 is set for 
5 watts out, the PA +V is not connected so its just a passive RF feed 
through.

The problem is that it is not possible to null out the reflected component 
even though the rig is connected to a 50 ohm dummy load.  Specifically the 
forward voltage at D16 anode is 9vpp and the reflected voltage is 1.5 vpp at 
D17 anode. Adjusting C1 appropriately adjusted the reflected voltage but does 
not reduce this voltage any lower than this.  Transformer T4 looks fine, the 
soldering is good and it appears to be in the circuit correctly.  The 
surrounding components (C1 C95 R28 R29) also look OK.  

Any ideas? Has anyone had a similar problem ?????

Thanks in advance and 73.
Jim WA2UMP K2:2679 


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