using an external supply with batteries in unit

[Alan Beck]

Hi,

I am running my KX1 off of a 12 Volt supply right now and leaving the
batteries in the unit.

I assume the purpose of D2 and D3 is to isolate the power jack from the
batteries when power is applied to the Jack?

Sure looks like it.

73
Alan
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[Ron D'Eau Claire-2]

That's right, Alan. You can safely connect an external power supply with the
internal batteries installed. The KX1 will draw power from whichever has the
higher voltage, the internal battery or the external power supply.

Of course, that will be the external supply normally, unless you are using a
very low-voltage supply for some reason.

Ron AC7AC

-----Original Message-----

Hi,

I am running my KX1 off of a 12 Volt supply right now and leaving the
batteries in the unit.

I assume the purpose of D2 and D3 is to isolate the power jack from the
batteries when power is applied to the Jack?

Sure looks like it.

73
Alan


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[W0rw]

If your external battery voltage goes below the internal battery
voltage, the internal batteries will start draining.
i left my KX1 on for a few days and after i ran down the external battery the
internal batteries took over and became totally discharged.
These were the expensive Lithium "AA" Primary batteries (L91's).
i wanted to save the use of these Li batteries for special uses.

The original power distribution design "AND's" the internal battery and
external battery sources together using 2 diodes.
You can change the power switching of J1 to prevent this.

Here are the details of the DC J1 switching Modification:
The Elecraft DC Power connector has an unused (normally closed) switch.
This modification will use that switch so that when an external power source
is connected the internal batteries will be disconnected, and conversely when
the DC power plug is removed the internal batteries will be reconnected.
Open the unit on an ESD grounded work station.
Separate the battery compartment by pulling the battery connector (J1) out.
Cut the 2 traces that ground P1-2 "-" (getting scary now)...Top Side..
Now add an insulated jumper wire from P1-2  "-" to the side contact of J1 (J1
is the power connector), The unused switch contact is soldered to an isolated
pad just the left of the marking 'Z2'...
That's it....
This will protect those internal batteries from discharging.

One other thing that you can do is to set the LED Display Control to "INF"
then the LED display will act as a pilot light.
72  de w0rw
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