[Elecraft] KAT2 Problem

[Masleid, Michael A.]

Hi Tom,

>T1 was correct but I pulled it and rewound it yet again.  Windings were =

>not shorted together.  Leads were tinned good.  Even yanked lead 3 to=20
>make sure there was no short when mounted on the board.  Still acts the =

>same.

Sorry your having trouble.  Sounds like your still stuck
trying to get the forward power measurement circuit working.

I figure that R6 is not installed.  So, when you go into TUNE,
the K2 is still using the circuits on the RF board to measure
power out level.

I figure that the K2 is making 5 watts - that DC current is
up over 1 amp.

I figure that you have a good dummy load on ANTENNA 1 and you have
antenna 1 selected.

I figure that you did the null adjustment, C55, and had a little
trouble getting a reading of zero - somewhere around 10 is the
best you got.  (That is normal - is that what happened on yours?)

As to the expected value at the top of R1: That should also be
3 to 4 volts with 5 watts into the ATU.

I don't know if you have checked the top of R2.  That should
indicate reflected power.  You should not see much voltage there.
I'd guess less than a volt.  Find some way to get a little
reflected power - perhaps a 500 ohm dummy load.  Make sure that
the voltage at R2 goes up.  Figure that you should see 3 to 4
volts at R2 with no load connected on antenna 1 with 5 watts in.
Of course, the K2 won't like that very much.

If the reflected power, REFL, pin 4 on U1, shows reasonable changes
when the dummy load is changed - say .8 volts with 50 ohms dummy
load at 5 watts with R1 and R2 fully clockwise, and say 3 to 4 volts
with a high VSWR dummy load, then the reflected power part of the
SWR bridge is working.  In that case, if FWD is still
down around 0.8 volts, figure that D1 may be bad.  (Sometimes the =
reverse
breakdown voltage on the 1N5711 diodes is ruined due to electrostatic
discharge or something.)

On the other hand, if REFL doesn't do much of anything, then perhaps
R3 is shorted out some how, or the RF path through the ATU to antenna 1
is blocked.  That should have caused odd readings when you did the null
adjustment.

73 and GL, de Michael, AB9GV