[Elecraft] KX3 charger failure?

[Rich NE1EE]

I just downloaded the schematic from the Elecraft site. I think this style of schematic, while space-saving, is difficult to read.
On p 9 @ B5, please find J1.
9-15VDC.
There you will see D6. I was expecting a different circuit, one that fed BAT+ and 15V+ each through a diode. That would provide a diode drop for each device, and provide reverse polarity protection.

If you are supplying 13.8V, the KX3 should report about 0.3-0.4V less. These are likely low forward drop diodes.

Even so, I am guessing that this is the correct place to look. Your problem suggests that if the voltage drops when good batteries are inserted, and pops back to 13.8Vdc when they are disconnected, then the problem might be in the charging logic. Some device may be making active choices for when to charge and when not to, and how much.

More than that is out of my league...

On 2020-10-09 00:23:+0200, István Szabó wrote:
>Rich, this is correct. I do not see diode on the charger board circuit diagram. I am lost.
>73, István
>
>On Thu, 8 Oct 2020 at 20:33, Rich NE1EE <<mailto:73.de.ne1ee at gmail.com>73.de.ne1ee at gmail.com> wrote:
>I am missing a point:
>Istvan said When I plug in the 13.8V PS the radio shows 13.8V for only 1 second and drops to 10.4V.
>Don replied so the fact that the KX3 shows 0.3 to 0.4 volts lower than the external supply is normal.
>
>Istvan said When batteries removed the voltage shown on display 13.8V.
>
>I don't have a KX3, but I understand the diode issue..and it makes sense...but a drop from 13.8 to 10.4 doesn't seem right to me.
>
>On 2020-10-08 18:56:+0200, István Szabó wrote:
>>On Thu, 8 Oct 2020 at 15:58, Don Wilhelm <<mailto:donwilh at embarqmail.com>donwilh at embarqmail.com> wrote:
>>
>>> Istvan,
>>
>>> There are protective diodes in series with both the internal batteries
>>> and the external supply, so the fact that the KX3 shows 0.3 to 0.4 volts
>>> lower than the external supply is normal.
>>
>>> 73,
>>> Don W3FPR
>>
>>> On 10/8/2020 2:53 AM, István Szabó wrote:
>>> > When I plug in the 13.8V PS the radio shows 13.8V for only 1 second and
>>> > drops to 10.4V. Eneloop batteries all OK 1.29V individually. Running a 4
>>> > hour charging cycle it turns off when voltage reached and shows the
>>> > dropped voltage. When batteries removed the voltage shown on display
>>> 13.8V.
>>> > Is it known failure, what can I do to fix it?