KPA/KAT500 Mystery Fail

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KPA/KAT500 Mystery Fail

kd4iz
All,

 

I have been using the KPA500/KAT500 combo with an IC-7300 and an IC-7100 for
around a year now. They are cabled and configured as per the Elecraft device
manuals. The cabling is identical for the two transmitters (actually, I use
the same 2 cables for both). All has been working properly with both radios
until very recently. The amp and the tuner continue to behave properly with
the 7300. The KAT500 continues to work perfectly with the 7100, however the
KPA500 no longer band switches when I change bands on the 7100 and key up.
In addition, the amplifier will not key. The 7100 still can put out full
power with the KAT500 in line. I have not changed any setting in any of the
3 devices to my knowledge. It is like the KPA500 has become deaf to the
IC-7100.

 

After switching back and forth and looking at all device settings, I am
baffled at this point! Is there anything in the way of rig to amplifier line
signals that could inhibit band switching by the amplifier but not by the
antenna tuner?

 

Thanks for your thoughts.

 

KD4IZ

Jack Spitznagel

FM19oo

 

 

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Re: KPA/KAT500 Mystery Fail

wa2lbi@gmail.com
Jack,

I assume the two cables you use are the RF coax cable and the PTT keying
line, correct?  The keying line should connect from the rig, then to the
KAT500, and finally the KPA500.  This allows the KAT500 to disable the
keying for the KPA500 during tuning or high SWR conditions.

It is possible that with moving the cables between the two rigs the keying
line cable has been damaged.  I have seen this before where a cable works
fine in one jack but not in another.  It is a matter of the cable being in
just the right position.  If you rotate it slightly it goes OC (Open
Circuit).

To simplify troubleshooting I would eliminate the KAT500 and plug the
keying line directly from the IC-7100 into the KPA500.  Put the amp on a
dummy load.

You said the '7100 doesn't key the KPA500.  You can check the KPA500
display for an asterisk (*) on the left side indicating that the amp is
receiving a keying signal (contact closure to ground) from the rig
('7100).  If you do not see that asterisk (*) then the amp is not  being
keyed by the rig.  Try a different cable to the rig.

If that doesn't work then try leaving the keying cable plugged into the amp
and unplugging the cable from the rig.  Touch to ground the center
conductor of the end of the cable you removed from the rig.  It should key
the amp and show the asterisk (*) in the display.  If the amp keys with the
cable grounded then it it time to look at the keying jack/circuit of the IC
-7100.

Let us know what you find.

Ken
WA2LBI





On Sun, Mar 10, 2019 at 10:28 AM <[hidden email]> wrote:

> All,
>
> I have been using the KPA500/KAT500 combo with an IC-7300 and an IC-7100
> for
> around a year now. They are cabled and configured as per the Elecraft
> device
> manuals. The cabling is identical for the two transmitters (actually, I use
> the same 2 cables for both). All has been working properly with both radios
> until very recently. The amp and the tuner continue to behave properly with
> the 7300.



> The KAT500 continues to work perfectly with the 7100, however the
> KPA500 no longer band switches when I change bands on the 7100 and key up.
> In addition, the amplifier will not key. The 7100 still can put out full
> power with the KAT500 in line. I have not changed any setting in any of the
> 3 devices to my knowledge. It is like the KPA500 has become deaf to the
> IC-7100.
>
> After switching back and forth and looking at all device settings, I am
> baffled at this point! Is there anything in the way of rig to amplifier
> line
> signals that could inhibit band switching by the amplifier but not by the
> antenna tuner?
>
> Thanks for your thoughts.
>
> KD4IZ
>
> Jack Spitznagel
>
> FM19oo
>
>
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Re: KPA/KAT500 Mystery Fail

kd4iz
Hi Ken, All,

 

Mike, N6MKF, sent me a direct email recommending that I try cleaning the connectors. I followed his recommendations again. No joy.

 

The 7100 does not behave as a “generic” rig. Remember that the more recent ICOM’s all use a 4 pin Molex for their ATU connection and have a 13 pin DIN connector that has all the other coding data and audio on it. Please see the cabling instructions on pages 8-10 in the KAT500 manual to see the wiring I use.

 

I checked the RF run: The coax cable is connected through an antenna switch to the KPA500 which in turn runs to the ATU. If I by pass the switch, the behavior is the same. AFAICT that path is fine.

 

The * (asterisk) does not show when the 7100 is keyed, so it appears that either the 7100’s HSEND line in the 13 pin DIN or the KEY line in the Molex is the issue. Basically the KEY line is the not the only key line signal… and HSEND is “bi-directional” so that complicates things. I am not sure which one is routed to the KPA (or if they interact somehow).

 

I know the KPA/KAT side is behaving as it should because they work with the 7300, so I will check both lines in both rigs and compare what they do when keyed. Probably the only way to tell if something needs repair or a connector is not making contact in the 7100.

 

Thanks for thinking this through with me.

 

KD4IZ

Jack Spitznagel

FM19oo

 

 

 

 

From: Ken Winterling <[hidden email]>
Sent: Sunday, March 10, 2019 11:33
To: [hidden email]
Cc: Elecraft Reflector <[hidden email]>
Subject: Re: [Elecraft] KPA/KAT500 Mystery Fail

 

Jack,

 

I assume the two cables you use are the RF coax cable and the PTT keying line, correct?  The keying line should connect from the rig, then to the KAT500, and finally the KPA500.  This allows the KAT500 to disable the keying for the KPA500 during tuning or high SWR conditions.

 

It is possible that with moving the cables between the two rigs the keying line cable has been damaged.  I have seen this before where a cable works fine in one jack but not in another.  It is a matter of the cable being in just the right position.  If you rotate it slightly it goes OC (Open Circuit).

 

To simplify troubleshooting I would eliminate the KAT500 and plug the keying line directly from the IC-7100 into the KPA500.  Put the amp on a dummy load.

 

You said the '7100 doesn't key the KPA500.  You can check the KPA500 display for an asterisk (*) on the left side indicating that the amp is receiving a keying signal (contact closure to ground) from the rig ('7100).  If you do not see that asterisk (*) then the amp is not  being keyed by the rig.  Try a different cable to the rig.  

 

If that doesn't work then try leaving the keying cable plugged into the amp and unplugging the cable from the rig.  Touch to ground the center conductor of the end of the cable you removed from the rig.  It should key the amp and show the asterisk (*) in the display.  If the amp keys with the cable grounded then it it time to look at the keying jack/circuit of the IC-7100.

 

Let us know what you find.

 

Ken

WA2LBI

 

 

 

 

On Sun, Mar 10, 2019 at 10:28 AM < > wrote:

All,

I have been using the KPA500/KAT500 combo with an IC-7300 and an IC-7100 for
around a year now. They are cabled and configured as per the Elecraft device
manuals. The cabling is identical for the two transmitters (actually, I use
the same 2 cables for both). All has been working properly with both radios
until very recently. The amp and the tuner continue to behave properly with
the 7300.

 

The KAT500 continues to work perfectly with the 7100, however the
KPA500 no longer band switches when I change bands on the 7100 and key up.
In addition, the amplifier will not key. The 7100 still can put out full
power with the KAT500 in line. I have not changed any setting in any of the
3 devices to my knowledge. It is like the KPA500 has become deaf to the
IC-7100.

After switching back and forth and looking at all device settings, I am
baffled at this point! Is there anything in the way of rig to amplifier line
signals that could inhibit band switching by the amplifier but not by the
antenna tuner?

Thanks for your thoughts.

KD4IZ

Jack Spitznagel

FM19oo

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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