[Elecraft] KPA100 SWR adjustment problem

Sat Jul 6 15:24:04 2002

Andrew,

Check T4 for correct orientation of the leads.  This torroid is part of
the RF and SWR sensing circuits and it is critical that it be properlly
installed.  If the leads are correct, check for <1 ohm between pads 1 & 4
of T4.  Do not test with your DMM probes touching the wires.  Also,
R26/27 should be at their mid-points for the SWR calibration, they will
be adjusted in a later step using a calibrated wattmeter.

73,
Mike WA3KYY

On Fri, 5 Jul 2002 23:19:23 -0600 "Andrew" <[email protected]>
writes:
> I got to the part during KPA100 assembly where the SWR reading is 
> adjusted.  With a 20W 50 ohm dummy load that has been tested good on 
> other rigs, the K2 (with KPA100 attached) gives a 0.1 9.9-1 reading 
> in tune mode with the power control set to 5.0 W.  The lowest SWR 
> reading I can get by adjusting C1 is 7.0-1 (actually the only two 
> readings I can get are 9.9-1 and 7.0-1, nothing in between).  By 
> turning R26 and R27 fully counterclockwise, I can get a reading of 
> 1.0-1, but the forward power remains at 0.1.  When I hook a DMM up 
> to U5 pin 1, I see a minimum of about 35 mV with R26 and 27 at their 
> midpoints, and a min. of 4.5 mV with R26/27 fully counterclockwise.  
> Receive seems to be fine on all bands with the antenna hooked up to 
> the KPA100's jack.  Current in tune mode is about 900 mA, and about 
> 400 mA in receive mode.  All of the tests done on the KPA100 up to 
> this point have been fine, but I have not yet done any voltage 
> checks (except the ones done during normal assembly).  Does anybody 
> have any ideas?
> 
> Thanks & 73,
> Andrew AC7CF
> K2 1637
> K1 508 
> 
> 
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