A week or so ago someone was trying to start a QMX using a current-limited bench power supply.? He chose his amperage limit appropriately, 250 mA if I recall correctly, but his voltage setting was 5.6 volts.?? Hans suggested upping that to 6 volts so the microprocessor could get the SMPS switch mode power supplies enabled.? I believe that fixed the immediate problem.? His build had several problems so at that time he said his board was dead.
/g/QRPLabs/message/107663

What voltage are you supplying?

Hi Ron,

I finally got around to replacing the older chip in the QCX-mini. Indeed, it now transmits CW (I haven't tested WSPR mode yet).

Thank you for your help!

-Bob

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Dr. Pedro,

As Ton pointed out, the notes are next to the version download.? The transmitter timeout was done on cessation of audio from the PC.?

?1_04 - 50 millisecond transmit timeout on cessation of audio from PC (protects QDX e.g. if PC crashes).

73
Evan
AC9TU

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Bruce
0 amps i press on button and 160ma and PC picks up QMX,? i load software and the LCD lights up and shows clearly the splash screen.? if i do nothing it stays like that (lcd on and splash screen) so i unplug power.
now 0 amps press on button and 160ma and nothing else no lcd light or any text.? if i start again and load software again lcd and splash screen appear. But i cant get any further than this.

Description with each firmware version?
73 Ton PA0ARR?

Hi,

I'm looking, but unable to find, the contents of each firmware upgrade of the QDX transceiver; sort of a release note of each one.

Specifically I'm looking for a correction of a problem of the early versions of the transceiver where if the controlling software dies while the transmitter is on it was kept transmitting, potentially causing harm to the finals if not noticed quickly and manually corrected.

I didn't experienced it lately but it might be just some luck that the infrequent hangs of the controlling computer (a Raspberry Pi 4) might not be sync-ed with a transmission moment.

If such fix were introduced, I would like to understand since which version (I might have it covered already).

Thanks! 73 de Pedro LU7DZ

Hans, I agree about the component failure scenario being unlikely.
I assume that the PWM signal is generated by a HW timer, you are not running a 166 kHz interrupt...
What if the software crash writes to the timer configuration registers and changes the function to a normal output?
Do you have a comment to making ghe? PWM signal AC-coupled?

73 de SM5EIE /Gunnar

Michael, not sure I understand - does the splash screen still show or did it only show one time?? What is the value of the current draw?? You can easily check to see if the 3 volt supply is working by using a ground on any of the connectors and probing any of the resistors on the control board.? With nothing pressed they should show ~3 volts.? This, of course, after power on button is pressed and released.

Colin i thought the same,
Hans posted (#103064)

1. Initialize the Flash memory, reset peripherals, configure the system clock, configure the I/O pins
2. Initialize the DMA (Direct Memory Access interface)?
3. Initialize the ADC (Analog to Digital Converter) of the CPU; we use 10 channels for monitoring supply voltage, 3.3V, 5V and Bias buck converter outputs, Fwd/Rev power from the SWR bridge etc; all continuously read via the ADC and stored in memory using DMA
4. SMPS (Switched Mode Power Supplies) initialization - this means the little plug-in buck converter boards.?
5. DIsplay init - which initializes the LCD module, switches on the backlight (depending on if you configured that to be on in the configuration menu), and writes the Splash screen text (QMX, firmware version, QRP Labs 2023).?
6. Blah blah loads and loads of other things - including eventually, the USB initialization...?
7. Eventually, audio system initialization (the I2S 48ksps stereo ADC chip and corresponding stereo DAC chip

I seem to be at 5
Switches on the back light and writes the splash screen
the SMPS come before this so thats what puzzels me about what direction to go next

I got the 2M low pass filter and seems pretty straight forward, except one line...

" The middle coil should be a little longer (for lower inductance)."

What does longer mean? Wider spread on the coils? taller leads so it stands further/taller on the board?

Bob
KG5GTE

Rick,
I will repair the board with an axial lead zener of higher power rating and put a ceramic capacitor in place of C107.
Then I will fit a large electrolytic somewhere on the main board.
I will do a simulation of AC-coupling the PWM signal before deciding if I do that modification

73 de SM5EIE /Gunnar

This sounds like it is hanging waiting for the switching regulator to spin up. It will pause the boot sequence till the voltages are correct and the switching regulator duty cycle is in the expected range. Then the current should drop to about 80ma. Hans has written about the a couple of times. Finding his description will give some places to probe.?
--
Colin - K6JTH?

Hi Chris,
thanks for sharing the spectrum images.

Although my comment is not useful for you here, I am glad about this publication, because it gives me the opportunity to compare my own measurements with the FA-NWT plus. The conditions are similar: 38 dB attenuator, but only 9 V voltage supply.

Here are my measurements for 80, 60 and 40 m:

Daniel, I dont agree...
The resistance of L101 is 2 Ohm and with a good short circuit in C107 and D108 the voltage rise will be limited by the voltage drop over L101.
If the supply voltage is disconnected fast enough the damage should hopefully be limited to C107 and D108
To operate a 6.3V tantalum capacitor at 5V should not lead to a failure, unless the capacitor is faulty

73, Gunnar SM5EIE?

Agree

It is definitely the case that Tantalum caps do that, surprisingly frequently and without much provocation
Unfortunately when they let go, like a Lithium battery there is a self fuelling exothermic reaction that has nothing to do with the applied power

Bad batch of caps ?

I would prefer to see an aluminium electrolytic to supply the uF and a parallel ceramic to handle the higher frequencies

Rick