[Elecraft] KAT2 Null Bridge Adjustment Problems

[Carl J. Denbow]

Thanks to everyone who gave me suggestions about how to troubleshoot 
this problem.  It has now been solved, and the solution was not as 
esoteric as one might have imagined.  I had a friend, who has built a 
number of Elecraft kits, look over my KAT2.  He discovered that I had 
left out R3!   Now, once that resistor was in place the readings nulled 
appropriately.  Why I left that resistor out during construction I have 
no idea.  It took another set of eyes to discover my omission.  The KAT2 
is now calibrated and working quite well.  Again, thanks to all who 
offered help.  This is a great list with great people!

73,

Carl
N8VZ

k4zm wrote:

> I've built the KAT2 and have become "stuck" at the Bull Bridge
> Adjustment stage (P. 16 Rev. D Manual).  No matter where I place the
> trim capacitor C55, I get "Hi" on the screen when I do a Tune in CALn
> mode.
>
>
>
> Carl:
>
> I usually make this adjustment using an old analog voltmeter on the 
> lowest dc votage scale.  You can see the null much easier.  I connect 
> the meter negative lead to ground and the postive meter lead to pin 4 
> of U1.  Then follow the directions in the manual.  If it will not null 
> then you probably have a problem with T1.  I would guess that 95% of 
> the problems with a null function are caused by T1 problems. (poorly 
> tinned transformer leads, the omission of the link between pins 5 & 6 
> of T1 and the leads of T1 not installed in the correct holes in the 
> board)
>
> 73
>
> Jim Younce K4ZM
> K2  SN: 18
>
>
>
>