Hello Greg,

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I am using rev 1.

The USB cables should be fully data i used them for my NanoVNA

i used Windows 10.

Tried also an older Mac with an older OS.

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No luck so far.

73

hanz YL3JD?

Hello Greg,

Many thanks for your points, i check it tonight. Now at work :-)

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Thanks 73 hanz

I have superficially similar behavior on 6m (QMX+ rev1).

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But I have not gotten around to troubleshooting it since I don't use 6m too often.

Replacing the PCM1804 is beyond what I would normally consider as a try-and-see experiment but it may come to that.

Please share what you find out.

Thanks.

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73, Mike KK7ER

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Thanks Nick,

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This is what i measured on JP104

See picture with the numbers at the measure points:

1. used as grnd

2. 6,9V

3. 7,7V

4. 1,14

5. 3V

6. ?0V

I hope this makes sense.

I feed the QMX with 8V

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Good? morning Hanz

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I've been watching this thread and have some comments and questions.

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1) What revision is your QMX?

2) Are the USB cables you are using known to be fully data capable??

--- There are a LOT of USB cables out there that only deliver power and not data.?

--- You absolutely need USB cables that have the data lines included.

3) You mentioned you tried a windows PC. What OS level are you using. You made need a USB driver for pre-Windows 10.?

4) As others have noted, that amount of current seems to indicate that the QMX is in bootloader mode (no firmware installed - earlier revision QMXs require you to first load the firmware. Also, if not a 'newer' revision unit that had the firmware pre-loaded from the factory folks, there won't be anything on the LCD display.

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5) So . . . in bootloader mode, you won't see a USB 'port' device. The QMX should appear as a Flash Drive.?

---On Windows, (depending on the OS version, etc) the flash drive may pop-up automatically or? . . .?

--- you may have to find the new 'drive' that appears in the Windows File Explorer and click on it to open the 'drive' window for copying in the firmware.

--- if you get that far, remember that you have to download the firmware and un-zip it. Then drag the file or copy and paste it into the flash drive window.

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Then power cycle the QMX one more time.? If all goes well, the LCD should come up with a band selection showing. You might have to adjust the contrast pot to get the characters to show on the LCD.

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here's a snip from the assembly manual.

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On booting up for the first time, the QMX screen contrast adjustment will be required; QMX
will then ask you for your choice of version, use the right-hand rotary encoder to select the
version you built (for example 80-20m) then press the left button to select it. If you chose
the wrong band version, you can always get back to this selection using by executing a
Factory Reset. Please refer to the operating manual for further details.Rotate the right encoder (I think its the right - might be the left) until you get to the selection that matches the version you assembled.?

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Hope this helps . . .

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73 GREG? KI4NVX

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Thanks Bruce and Ronan,

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I was a bit confused by 74ACT08SC and 74ACT08SCX. One in SOIC-14NB and one in SOIC-14. Only a small difference in some geometrical parameters, but maybe important for QMX. So I remembered the post about an alternative IC.

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Ronan, it was the MC74ACT08... MC74ACT08DG is in SOIC-14. That should be my choice.

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73 Ludwig

Is the 3.3V VDD rail present Hanz?

p.s. i use 8volts as power

Hello Nick,

It still draws 150mA when a push the encoder. I tried what you wrote but the computer still does not see a USB.

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Difficult issue.

73

hanz

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On Mon, Jan 6, 2025 at 06:09 PM, Ed Kwik wrote:

Dan,

Are you bringing it to FDIM?

Ed

AB8DF

On Jan 6, 2025, at 5:58 PM, Daniel Conklin via <danconklin2@...> wrote:

I still have one of those I built into an Altoid tin. Mine is in 20 meters, but it chirps a bit.?

--

73, Dan - W2DLC

Ed,

No, I wish I could go to one of those, but I have to work. I don't have much time for ham radio these days.?

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73, Dan - W2DLC

When you say ‘now nothing happens anymore’ do you mean the QMX is now no longer drawing power when you push the encoder button, or is it completely dead.

the USB socket on the circuit diagram is J201 and the two USB data lines feed directly into the processor, there is no additional circuitry. As others have said the VBus from the computer side of the QMX is not connected, only the data lines.

If the QMX still shows a current draw when you push the encoder, plug the usb cable from the QMX into your computer, before you try to power up the QMX, then once connected try to power up the QMX.

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If the QMX is completely dead, you need to start looking at the power on arrangement, note that while in Bootloader mode the SMPS are not enabled, only the linear 3.3V regulator is used to power the CPU.

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There is an explanation in the wiki.

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73 Nick G0OQK

Rob, this has been discussed on the group here previously, this is a common outcome for the high band QDX builds, my rev 5 was this way, too. 20 and 17m share the same BPF, and there's interactions between the other BPF slots, extra capacitance from the PCB, and more. Hans has stated this is a compromise that had to be made to fit all bands in. This is part of why the QMX midband uses 2 separate toroids for the BPF, and the QMX+ uses only 2 bands per BPF toroid....it helps keep the BPF slots from interacting with each other. I think Hans may have softened the L-C sharpness of the BPF values in general, too...but not positive.?

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I use a low band QDX and my high band QDX on the same antenna, and I just increased the audio level on the high band...it's not really noticeably worse in reception on 20m.?

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I struggled to make some of the bands sweep well with a mid-band QDX I built (40-15m), and ended up just bypassing the BPF entirely, and run a K9DP BCI filter in front of the QDX for <3.5 mhz. So far has worked fine in the US.

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-Nate

N8BTR

dr operators,

I checked the 5 volts on the usb connections on the pcb.

A4 A9 B4 and B9 measure 5 volts.(see enclosed documents).

I see no splashes of solder.

I tried an other USB cable.

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I try to find the USB section in the circuit schematic but can not find it.

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Does any one has an idea what i can check next?

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73 hanz

I ordered mine from Farnell.? The part number was MC74ACT08DG manufactured by ONSEMI.?

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Cheers,?

Ronan

MM0IVR?

many thanks for the suggestions, i did a lot of checking and used 2 cables.?

i will focus on the power of the usb, now knowing it is separate from the power of the qmx.

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many thanks will let know what i find.

73 hanz

I had a QMX+ (rev 2) I recently repaired that had a similar symptom. ?A tone was present on some bands but not others. ?There was also a bit more noise than usual. ?This is all with a dummy load attached. ?The A/D sweeps all looked good. ? I replaced the PCM1804 A/D converter chip and it completely resolved the issue. ?

I’m not saying this is your problem. ?But it’s an idea to try.

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--

73
Jeff Moore
W1NC

Hanz,

The USB power lines are not connected inside the QMX so I suggest you try another USB cable or investigate the soldering around the USB socket on the mainboard.

73

--

David Thomas M0OOR