[Collins] KWM-2 Repair or HELP Needed!

[Roger Shultz]

Normally I can fix any Collins A line radio but in the case of my KWM-2, I
just don't want to! It has frustrated me to a point where someone with less
emotion could surely do the job better so I would appreciate references off
list of suggested resources here in the northeast (NJ) if possible.

The problem  is a transmit problem that manifests itself in several ways.

The first problem is that 80 meters particularly seems to be very sensitive
in terms of getting grid drive.

I found that work has been done previously in the 80 meter mixer plate area
but it appears to have been done OK though the trimmer and parallel cap was
replaced suggesting this problem was around long before I bought it. If I
tune the exciter tuning very slowly grid drive will literally "pop" up and
as I go past peak it drops and can't be found until I slowly tune from lower
in frequency to higher in frequency.

Additionally, while I have gotten as much as 110 watts out on 80, I can't
get more than 70 watts on any other band. I have tried new finals, yes, they
are the 6146W's which are known problems in some radios, they are
neutralized  and screen and HV voltages are proper. 6146's do not seem to
change the output though I can;t be sure they are not  weak. Today, power
dropped down to 50 watts even on 80 meters. I do pull about 230 mils on
transmit so maybe the problem is in the pi-network output which has not been
checked.

Another screwy thing is there is some sort of intermittent that generates
"static" as I tune the exciter tuning but only when it is lying normally and
disappears when on its side! I have tightened the coils shields with no
change. I can tap the chassis and the static appears suggesting a loose
ground or some connection but because it goes away when flipped over I can't
find the darn thing!

Yet another problem that occurs only at times is that when I bring it back
from tune or lock key it takes a very long time to come back to receive,
like it has tons of AGC action going on. There is a SB that sounds like it
fits and the problem is said to be a screen grid problem in the PA and adds
a diode to correct it or suggests new finals but it sure is a nasty thing
when it happens and it is at times accompanied by audio feedback!

It receives quite well even on 80 meters suggesting the problem really is in
just a few stages. I may well be "dense" and stubborn but for the life of me
would it have hurt to put in some RF level measurements in the book to
enable troubleshooting an rf problem! The transmit level chart showing
signal generator measurements makes no sense to me either!

I apologize if this sounds like a tirade (which it is to a degree) hence one
may understand why I could use some help or if not just an outright 
admission
of defeat and let someone else fix this.

73, Roger, NJ2R