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KAT100 General Failure

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Jonathan Taylor, K1RFD

KAT100 General Failure

I am testing my KAT100, which had been sitting idle for a number of
years. It is connected to the K2/100 via the DB9 cable as described
in the KAT100 manual. The two are interconnected with a coax cable
and Ant1 is connected to a dummy load.

1. Apply power to KAT100.
2. Turn on K2/100.
3. Almost immediately, all LEDs on the SWR bar graph illuminate, the
S-meter bar graph on the K2 goes full scale, and both remain in this
state. The receiver is silent. (There is no indication of any output
power, as if it were transmitting.)

Pressing the ANT1-2 button on the K2 produces the "not inst" message.
Turning off the K2 power, all LEDs on the KAT100 remain illuminated.
With KAT100 powered off, K2 functions normally.

I have verified the wiring of the DB-9 cable. What's the next best
thing to check?

Thanks
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Don Wilhelm

Re: KAT100 General Failure

Johnathan,

Since the KAT100 is not recognized in the K2 menu, you either have a
problem with the KAT100 firmware, but do check the cable for continuity
of the AUXBUS signal that is used to communicate among the various
pieces of firmware ICs throughout the K2 system.

Since the KAT100 has not been in service for a while, it may be that
there is oxidation on the KAT100 firmware IC pins. Removing and
reinserting the firmware IC may bring it back to life by wiping away any
oxidation on the pins.

As for the LEDs, that is also controlled by the firmware IC, so fix the
firmware problem first, and then you can find any problems that remain.

73,
Don W3FPR

On 1/3/2020 11:13 PM, Jonathan Taylor, K1RFD wrote:

> I am testing my KAT100, which had been sitting idle for a number of
> years. It is connected to the K2/100 via the DB9 cable as described
> in the KAT100 manual. The two are interconnected with a coax cable
> and Ant1 is connected to a dummy load.
>
> 1. Apply power to KAT100.
> 2. Turn on K2/100.
> 3. Almost immediately, all LEDs on the SWR bar graph illuminate, the
> S-meter bar graph on the K2 goes full scale, and both remain in this
> state. The receiver is silent. (There is no indication of any output
> power, as if it were transmitting.)
>
> Pressing the ANT1-2 button on the K2 produces the "not inst" message.
> Turning off the K2 power, all LEDs on the KAT100 remain illuminated.
> With KAT100 powered off, K2 functions normally.
>
> I have verified the wiring of the DB-9 cable. What's the next best
> thing to check?
>
> Thanks
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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Jonathan Taylor, K1RFD

Re: KAT100 General Failure

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?

On Sat, Jan 4, 2020 at 9:54 AM Don Wilhelm <[hidden email]> wrote:

>
> Johnathan,
>
> Since the KAT100 is not recognized in the K2 menu, you either have a
> problem with the KAT100 firmware, but do check the cable for continuity
> of the AUXBUS signal that is used to communicate among the various
> pieces of firmware ICs throughout the K2 system.
>
> Since the KAT100 has not been in service for a while, it may be that
> there is oxidation on the KAT100 firmware IC pins. Removing and
> reinserting the firmware IC may bring it back to life by wiping away any
> oxidation on the pins.
>
> As for the LEDs, that is also controlled by the firmware IC, so fix the
> firmware problem first, and then you can find any problems that remain.
>
> 73,
> Don W3FPR
>
> On 1/3/2020 11:13 PM, Jonathan Taylor, K1RFD wrote:
> > I am testing my KAT100, which had been sitting idle for a number of
> > years. It is connected to the K2/100 via the DB9 cable as described
> > in the KAT100 manual. The two are interconnected with a coax cable
> > and Ant1 is connected to a dummy load.
> >
> > 1. Apply power to KAT100.
> > 2. Turn on K2/100.
> > 3. Almost immediately, all LEDs on the SWR bar graph illuminate, the
> > S-meter bar graph on the K2 goes full scale, and both remain in this
> > state. The receiver is silent. (There is no indication of any output
> > power, as if it were transmitting.)
> >
> > Pressing the ANT1-2 button on the K2 produces the "not inst" message.
> > Turning off the K2 power, all LEDs on the KAT100 remain illuminated.
> > With KAT100 powered off, K2 functions normally.
> >
> > I have verified the wiring of the DB-9 cable. What's the next best
> > thing to check?
> >
> > Thanks
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> > Message delivered to [hidden email]
> >

Don Wilhelm

Re: KAT100 General Failure

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?
>
>

Jonathan Taylor, K1RFD

Re: KAT100 General Failure

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 <[hidden email]> 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?
> >
> >
>

Don Wilhelm

Re: KAT100 General Failure

Jonathan,

That is a great discovery. Yes, if U5 was getting hot it would be
dragging down the 5 volt supply and causing U1 to not function.

73,
Don W3FPR

On 1/4/2020 12:18 PM, Jonathan Taylor, K1RFD wrote:

> 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
>
>