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Paul, the pictures are named by a letter (a ... n). I wonder where I could see these letters related to schematics. Fine, but did you set the oscilloscope channel to 10:1? This will show the right

I just received my pre-build 20-10 meter QMX and without thinking did a factory reset. Now the QMX only tunes 80-20 meters, not the original 20-10 meters as received from QRP Labs. Now, how to return

Minor correction: In? ?" Q110 has nothing to do with it.? Q100 loads up the 3V3 SMPS with 3.3v/47=70ma while it is starting up." Should read "Q110" instead of "Q100"

Nico, you should use a dummy load for testing. Which values when using a dummy load? Which output on different bands? With a very low output you may have unstable SWR values. Which output is shown by

I would verify that Q4 is working correctly.? A failed D5 would not exhibit the symptoms you are listing. Also, verify that there is no short to ground on the junction of L# and L$ when the mid band

Don could be right, the USB cable providing a needed ground return was my first thought. But Brian has moved to what looks like a properly isolated lab supply, and the problem persists. The reported

Sorry, no. Your 9 V shold be switched to the signal "+12V" feeding also IC101. To produce around 3 V at VDD the input voltage for IC101 must be at least around 5.5 V. You will find this reading the

Jerry, Thanks.? Now that I understand it a little better, I will take a look at this the next time it fails or the next time I have it apart. Brien -KE7WB

Brien, Worth looking at LIN_REG_EN with a voltmeter. However,?R101 should pull up LIN_REG_EN just fine, turning on Q102 to get "+12V" to U101 (the 78M33). At that point the processor starts running

Thanks Oley, I have never used Flrig even if it is installed in my computer. Could you, please, answer me with your settings in order that I can configure a working software? 73 - Pierre - FK8IH

But the USB connector DOES provide a ground return, that should be a clue. What happens if you provide an explicit ground from the power supply negative to the radio chassis, like the RF connector or

I'm still debugging my QDX Rev. 4. I have managed QSOs on 20m, receives on 30m, receives on 40m (once), power output on all bands. Now, the rig is no longer receiving or transmitting on any band.

After studying this a little further I am thinking LIN_REG_EN is not making it to the 3.3V supply. The the linear regulator could show the 3.3V when the knob is pressed but if it is not being passed

please see 'I have a craving...' 73, Wolfgang OE3WFA

Hi Lionel What voltage did you build? ?If it is a 12 volt build the output is reasonable. You need to use a 50 ohm dummy load when doing the sweeps. ?Otherwise the LPF is impacted by the impedance

Ludwig, After looking at the schematic I think I can come up with a plausible explanation for my symptoms. When the left knob is pressed it provides PWR_ON, passing the input voltage, in my case

Thanks Ivan ! Would have hoped though that the Tx is disabled when Rx is outside band. But maybe it isn't.... Cheers Gert

Hello Lionel, I just built a new QDX a few weeks ago and had a similar experience. The RF Sweep for 20m is flat across 14mhz and the power output is lower than described on the QRP Labs website. I

I just have a dipole in my room but I'm confused how it can all be 2 swr [email protected]> wrote:

Brian, Does sound like you know what you are doing. You have a very weird set of symptoms. I'm having a hard time imagining how plugging in the USB cable makes it work if there is a solid ground