[Elecraft] KAT2 Problem

[Masleid, Michael A.]

Hi Tom,

>Finally got the correct voltage following suggestions here and in the=20
>archives.  Something weird seems to be going on with C55.

>With the shaft slot parallel to the short edge of the board and the=20
>solder blob pointed at the adjacent short edge, I get more than enough=20
>voltage.  At the opposite position (solder blob pointed at opposite=20
>short edge) I get 0.7 volts.  Unfortunately it's at this point where I=20
>obtain the null.  I also noticed that the null doesn't seem to be=20
>stable.

Sounds like the T1 primary link winding is not going through T1,
(see the second step on page 6) or else there's a dead short across
the primary link on the circuit board, or a dead short between
T1's secondary pad 1 and pad 3 or pad 4.  The way the SWR bridge works
is to sample line current into a voltage using T1, added or subtracted
from the voltage off of C55.  About mid way on C55 you should get a =
null.
If there is no RF coming out of T1, then C55 will act the way you
describe, since there is nothing on the secondary of T1 to null out.

See if the voltage at R1 and at R2 are always the same - when R1 is at
3 volts, is R2 also at 3 volts?  When R1 is at 0.8 volts, is R2 also
at 0.8 volts?

Please verify that the resistance between the tops (diode side) of
R1 and R2 is zero ohms.  If not, there is a break in the wiring through
T1.  Now remove one lead on T1 - pad 1, 2, 3, or 4.  Make sure the
resistance is now 200 ohms between R1 and R2.  If not, there is a short
circuit across R3.

73, de Michael, AB9GV