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Hello all.

I bought a built QMX, being in my early 80s and not quite up to building a complex QRP Labs kit. When it arrived, I unpacked it and plugged in the PS IO use for the K3. Looking at the panel, I saw the blinking battery symbol and after some rtfming, plugged in a 12 VDC PS. However, the QMX+ has major problems, some as quirky as a sidetone which is sometimes there, sometimes not, and major problems such as it does not receive or transmit any RF energy (and it’s not in practice mode). Would ten seconds of 13.8 volts cause this amount of disfunction?

Thanks,

Dave K9SW

The QMX has a protection circuit that will shut off
the transmitter if the supply voltage is dangerously
high, or too low.

It will warn you by flashing the battery symbol on the
front panel.

I don't know if it is right, but if my QMX+ shuts the TX
down for high VSWR, it loses sidetone too.

The sidetone and the TX power won't come back until you
cycle the radio off and then back on.

Perhaps, the same is true for over voltage shutdown?

Try strapping on a dummy load, applying 12.0V cycling the
power, and see if your sidetone comes back.

The radio is not amused by over voltage, or over VSWR,
but it usually, it will survive if the insult isn't too
bad.

In any case, automotive batteries, and automotive chargers
are verboten for the QMX. It doesn't want to see anything
over 12.0V (9.0V if it was built for 9V).

-Chuck Harris, WA3UQV


On Mon, 13 Jan 2025 18:23:21 -0600 "K9SW via groups.io"
<K9SW@...> wrote:

Hello all.

I bought a built QMX, being in my early 80s and not quite up to
building a complex QRP Labs kit. When it arrived, I unpacked it and
plugged in the PS IO use for the K3. Looking at the panel, I saw the
blinking battery symbol and after some rtfming, plugged in a 12 VDC
PS. However, the QMX+ has major problems, some as quirky as a
sidetone which is sometimes there, sometimes not, and major problems
such as it does not receive or transmit any RF energy (and it’s not
in practice mode). Would ten seconds of 13.8 volts cause this
amount of disfunction?

Thanks,

Dave K9SW

Thanks, Chuck. I’ve tried many variations, factory reset, restarts, using SWR meter and dummy load, so no high SWR concerns. Still no output or input. I’ll work on it some more and see what else happens.

It came from Mugla with the sheet listing all the power outputs on each band, so it was transmitting at one time.

73,

Dave

Have you tried 12.0V?

-Chuck Harris, WA3UQV


On Tue, 14 Jan 2025 16:54:49 -0600 "K9SW via groups.io"
<K9SW@...> wrote:

Thanks, Chuck. I’ve tried many variations, factory reset, restarts,
using SWR meter and dummy load, so no high SWR concerns. Still no
output or input. I’ll work on it some more and see what else happens.

It came from Mugla with the sheet listing all the power outputs on
each band, so it was transmitting at one time.

73,

Dave

On Jan 14, 2025, at 6:37?AM, Chuck Harris via groups.io
<cfharris@...> wrote:

The QMX has a protection circuit that will shut off
the transmitter if the supply voltage is dangerously
high, or too low.

It will warn you by flashing the battery symbol on the
front panel.

I don't know if it is right, but if my QMX+ shuts the TX
down for high VSWR, it loses sidetone too.

The sidetone and the TX power won't come back until you
cycle the radio off and then back on.

Perhaps, the same is true for over voltage shutdown?

Try strapping on a dummy load, applying 12.0V cycling the
power, and see if your sidetone comes back.

The radio is not amused by over voltage, or over VSWR,
but it usually, it will survive if the insult isn't too
bad.

In any case, automotive batteries, and automotive chargers
are verboten for the QMX. It doesn't want to see anything
over 12.0V (9.0V if it was built for 9V).

-Chuck Harris, WA3UQV


On Mon, 13 Jan 2025 18:23:21 -0600 "K9SW via groups.io"
<K9SW@...> wrote:

Hello all.

I bought a built QMX, being in my early 80s and not quite up to
building a complex QRP Labs kit. When it arrived, I unpacked it
and plugged in the PS IO use for the K3. Looking at the panel, I
saw the blinking battery symbol and after some rtfming, plugged in
a 12 VDC PS. However, the QMX+ has major problems, some as quirky
as a sidetone which is sometimes there, sometimes not, and major
problems such as it does not receive or transmit any RF energy
(and it’s not in practice mode). Would ten seconds of 13.8 volts
cause this amount of disfunction?

Thanks,

Dave K9SW

After the initial fifteen seconds of 13.8 volts, I switched to 12 volts. Maybe I should try 9 volts.

Dave K9SW

12.0 should be fine, but note that power bricks, etc. that
say 12.0 put out anything but. Typically, 17, no load, and
drop down to 12.0 when some percentage of fully loaded.

... so, do measure your unloaded voltage.

The QMX+, default, is 13V for an over voltage trip, and
7V for low voltage trip.


On Tue, 14 Jan 2025 20:03:26 -0600 "K9SW via groups.io"
<K9SW@...> wrote:

After the initial fifteen seconds of 13.8 volts, I switched to 12
volts. Maybe I should try 9 volts.

Dave K9SW

On Jan 14, 2025, at 5:49?PM, Chuck Harris via groups.io
<cfharris@...> wrote:

Have you tried 12.0V?

-Chuck Harris, WA3UQV


On Tue, 14 Jan 2025 16:54:49 -0600 "K9SW via groups.io"
<K9SW@...> wrote:

Thanks, Chuck. I’ve tried many variations, factory reset,
restarts, using SWR meter and dummy load, so no high SWR concerns.
Still no output or input. I’ll work on it some more and see what
else happens.

It came from Mugla with the sheet listing all the power outputs on
each band, so it was transmitting at one time.

73,

Dave

On Jan 14, 2025, at 6:37?AM, Chuck Harris via groups.io
<cfharris@...> wrote:

The QMX has a protection circuit that will shut off
the transmitter if the supply voltage is dangerously
high, or too low.

It will warn you by flashing the battery symbol on the
front panel.

I don't know if it is right, but if my QMX+ shuts the TX
down for high VSWR, it loses sidetone too.

The sidetone and the TX power won't come back until you
cycle the radio off and then back on.

Perhaps, the same is true for over voltage shutdown?

Try strapping on a dummy load, applying 12.0V cycling the
power, and see if your sidetone comes back.

The radio is not amused by over voltage, or over VSWR,
but it usually, it will survive if the insult isn't too
bad.

In any case, automotive batteries, and automotive chargers
are verboten for the QMX. It doesn't want to see anything
over 12.0V (9.0V if it was built for 9V).

-Chuck Harris, WA3UQV


On Mon, 13 Jan 2025 18:23:21 -0600 "K9SW via groups.io"
<K9SW@...> wrote:

Hello all.

I bought a built QMX, being in my early 80s and not quite up to
building a complex QRP Labs kit. When it arrived, I unpacked it
and plugged in the PS IO use for the K3. Looking at the panel, I
saw the blinking battery symbol and after some rtfming, plugged
in a 12 VDC PS. However, the QMX+ has major problems, some as
quirky as a sidetone which is sometimes there, sometimes not,
and major problems such as it does not receive or transmit any
RF energy (and it’s not in practice mode). Would ten seconds
of 13.8 volts cause this amount of disfunction?

Thanks,

Dave K9SW