[Elecraft] KAT100 General Failure

[Jonathan Taylor, K1RFD]

Don,

Z1 is resonating away, but in the course of verifying that, I noticed
that the U5 op-amp was getting hot to the touch.  I replaced it, and
now all is working normally.  Perhaps it was loading down the 5V
supply excessively.

I'm guessing that U5 made the ultimate sacrifice in the same incident
that zapped D1 and D2 some years ago.  Apparently this has happened
before, because I see that I had installed an 8-pin DIP socket for it
:)

Thanks again for your help!

73
Jonathan K1RFD

On Sat, Jan 4, 2020 at 11:19 AM Don Wilhelm <donwilh at embarqmail.com> wrote:
>
> Jonathan,
>
> Yes, replacing KAT100 U1 would be the prudent first step.  But if you
> can, first determine if the resonator Z1 is providing clock pulses to U1
> pins 13 and 14.  Without those clock pulses, U1 will not be functional.
>
> If you have a local ham who also has a KAT100, see if you can swap U1
> from his KAT100 to see if U1 is the problem in yours.
>
> If you do not have a local who is willing to swap, then your best bet is
> to order both the firmware and the resonator from Elecraft.
>
> OTOH, if you have a 4 MHz resonator on hand, try replacing Z1 first to
> see if it comes back to life.  The resonator is inexpensive, but the
> firmware IC is costly.
>
> When the firmware is working, it will be recognized by the K2,
> regardless of any other problems that may be present with the KAT100
> operation.
>
> 73,
> Don W3FPR
>
> On 1/4/2020 10:49 AM, Jonathan Taylor, K1RFD wrote:
> > Thanks Don.
> >
> > I had the same thought about U1, but unfortunately the symptoms remain
> > after re-seating it a couple of times.
> >
> > Regarding AUXBUS, I believe continuity is good, since a logic probe on
> > the KAT100 side shows activity when certain K2 controls are
> > manipulated such as Power, Tune, and Band. It is "high" at all other
> > times. I checked this all the way to pin 40 of U1.
> >
> > Should I conclude that the next step would be to replace U1?
> >
> >
>