Re: QMX+ no power output, low SMPS bias current
I believe it said to 'solder' it under the board, not 'put' it under the board, which would mean soldering on top.?
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Re: QMX+ no power output, low SMPS bias current
I have successfully used the 330 ones from this Amazon kit:
It is best to use a hot air station to remove/replace, since the contacts are underneath.
I have an inexpensive hot air station, and mask off all nearby components (on both sides of the board) with aluminum tape or kapton tap to hold them in position while I do the hot air work, otherwise they may blow out of position, because their solder may also liquify.
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Re: QMX+ no power output, low SMPS bias current
Looks like the L501 is broken.? Guess I'm ordering parts, and trying again.
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Re: QMX+ no power output, low SMPS bias current
First a couple of basic checks on your measurement setup -
- make sure your scope and probes are set up correctly: most scope probes have a? 1x and 10x option, and it needs to match that same option on your scope, otherwise the readings will be incorrect by 10x
- when you measured the output, did you have a dummy load attached?? hopefully so, unless your scope has a 50-ohm termination option turned on (but most inexpensive scopes don't have an internal 50-ohm termination).
- when you measure, are you measuring peak-to-peak voltage of the sine wave, or an RMS value?? Most scopes report both; peak-to-peak is probably best for debugging
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If the above are done correctly, you are seeing very low power out of the QMX, but real power.? 4W out should be about 40Vp-p, but Tune SWR default is 50% voltage, so about 20Vp-p.?? The 5Vp-p you measured would be 62 milliwatts (5Vrms would be 100mW).?? So please first confirm your measurements.
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If they are correct, it means your BS170s are not amplifying the signal much, if at all - or maybe all your LPFs are turned off due to no bias current, so the signal isn't coming out.
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Most often we don't have a bias current problem, but Jeff has noted that sometimes the L501 gets broken (one of those 330uH coils), or C504 (the big tantalum capacitor) fails.? So you could check those two items.? Also check that L504 and L514 are soldered in properly and not cracked (since I understand they are a bit fragile) - and that your diodes are not soldered in backwards.? Any of these could cause havoc with the bias current.
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Stan KC7XE
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Re: QMX+ no power output, low SMPS bias current
In a spirit of double and triple checking everything, I rechecked continuity for my connections on T507 and T501.? T501 had intermittent continuity between two of the primary windings.? After reflowing the connections, I am now getting a signal out of the BNC connector when I hit Transmit and the SWR has stabilized going into the dummy load at close to 1.0 (except on 6m, which is fluctuating between 2 and 4).? However, I am still getting the extremely low SMPS bias current, and Diagnostics still reports 0W output.? The power meter on the dummy load is showing a little power output (possibly as high as 5W for 160m and 80m, but going down for successive bands).
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Re: 750 Hz Square Wave from #QMX Speaker while Transmitting
#qmx
#beacon
I suspect that the QMX hardware is generating the steady fixed volume 750 Hz square wave and outputing it through the earphone jack only during beacon transmissions.
This only occurs when the QMX is left in USB or LSB mode during the QMX's built-in beacon transmissions.
This report is merely an observation. There is no apparent malfunction as the transmitted beacon RF is a clean single frequency signal.
AD5DZ also reported observing 750 Hz square waves /g/QRPLabs/message/139807
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Re: Release of version 2.0 of ABS solution for QMX+ (Automatic internal antenna tuner, internal battery and internal speaker with audio amp)
#PSU
#QMXplus
#audio
#ABS
#ATU
Looking to start a very limited group buy in ZL for the boards only. The other components including hardware etc. Can be selfpurchased from Digikey for about NZD 70 WITH FREE SHIPPING The cost for five boards from JLPCB at today's exchange rate is approx NZD 470 including shipping from China making it approx NZD 92 each.
The order will include the ATU and audio board,? battery/speake board,, front and rear pcb panels.
The cost should cover domestic
shipping from my qth to non rural NZ.
We have three hands up and looking for two more to make it cost effective.
Any ZL QMX+ owners Looking to join please contact me
73
ZL1REY
USPS Shipping fee is US$50.55 to Austria.? I'm not sure if there is any customs fee; I think not, but maybe some.
But that is high enough that it negates the savings of a group-buy, so it would likely be more cost effective to order items directly.
Unless what you value is the convenience...
Stan
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Re: QMX shutting off at 10.5V
Chris, Ludwig,
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Thank you very much for your returns, now it starts to make sense to me. I won't have time to troubleshoot before this weekend as I am away but I am looking forward to the debugging. Right now I would put my money on something pulling down the 3.3V power supply but I could be wrong of course! I just hope that it isn't the microcontroller.
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73,
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Yannig F4IUJ
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Re: Available Hand Mics for QMX SSB ?
Got mine today. Very excited! Thanks, so much Erik!!!!
--
73 Michael N6QP
Up in Thin R
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Hello, I just completed a QMX build and had a power-up issue.
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I used a lab PSU at 7V initially; QMX draws ~150 mA right away - not proper.
But at the same it did power-up and display lights up.
So I tried USB connection and was able to flash the firmware successfully.
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- it self-turns on;
- MCU probably thinks it is underpowered: as soon as it boots and displays normal view, it shows "Shut down!" and cycles;
- display backlight blinks randomly - again, power stability issue?
- draws too much power: I dared to try to turn it on with 9V and got almost 1A consumption.
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I double-checked all components, especially on power boards and found no fried parts or soldering issues.
I also checked the 8-pin power board connector; it is the only board getting the incoming voltage, is this correct?
I don't see constant grounding on PWR_ON pin (unless left knob is pressed).
There's no measurable impedance between power and ground on the power connector if the power board is removed.
I also checked for notorious Q103/Q104 short before building - not a known V4 problem, but just in case.
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What else I can check? I assume the problem is within 8-pin power board; could it be somewhere else?
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Thank you in advance.
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Just finished my QMX+ and really enjoyed the build. Built a QDX a couple of years ago and it has been great.
Powered up at 9 volts and no smoke! Draws about 100 ma and audio out can be controlled and tune appears to work and mode / band does something. Connecting an antenna increases the noise so it appears the receiver is working.
But nothing appears on the display except for the backlight. Turned the pot from stop to stop with no results.
I’m going to touch up all 16 of the display header pins. What a bad place for a soon to be 83 year old duffer to be soldering. Why couldn’t that bave been added to the display board before mounting?
Any other thots?
72/73
Jim w0nkn
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Re: Internal mic seems to be working?
#qmx
#ssb
While I'm not sure how bad it sounds on the other station, and I understand that it is less than ideal, I was able to make another SSB contact over the weekend using the internal mic. The station in UT gave me 53 and my report was 55.
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Since the internal mic is enabled for noise input, I think it still works when used alone without the external mic. Of course the sound may not be so good without noise cancellation.
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73,
Yoon KM6KJI
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Re: QMX+ no power output, low SMPS bias current
I picked up an oscilloscope multimeter, (50MHz bandwidth) and checked the signal coming out of the QMX+ and got some interesting results.? When I tried to transmit through the Diagnostics in the Terminal, I got nothing, but when I used the Tune SWR function, I got clear sine waves on every band except 6m (to be expected as it's outside the bandwidth of the scope).? On 160m and 80m, for example, it was a roughly 1V signal.? On 60m it was closer to 5V.
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It's been decades since I did any EE in college, and signals processing/RF was never my strong suit.? What else should I be looking at?
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Just finished "building" my QMX+ and everything works as advertised! Got lazy and tried a couple of FT8 contacts on 20. Kentucky, Indiana and Brazil in short order on an end-fed dipole.
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I'm impressed, Hans. Thank you for the contributions you've made to the community.
--
Brent DeWitt, AB1LF
Milford, MA
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What bands on the qdx?
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Larry
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Re: Available Hand Mics for QMX SSB ?
Found this information ( for connecting a computer headset to the 705, it shows the schematic for connecting the condenser mic element and a switch to the 705 as follows:  If this information is accurate, the ground side of the mic and PTT is the sleeve on the mic, the PTT button is the TIP and the mic is the RING.. so, making an adaptor that places the 0.001uF and 330pF across the RING and SLEEVE, connecting the 2.2K resistor to ring on mic and Ring1 on IC-705, a 1uF cap from ring on mic to TIP on 705, and to a 33K resistor that connects to TIP on mic should do the trick.
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Re: Available Hand Mics for QMX SSB ?
It will take more circuitry than just connections. The 705 has the phantom power separate from the mic+ line and the PTT connected to the mic+. That is completely different from how QMX works, where phantom power for electret is present on mic+ and PTT is separate contact. You'll probably need a couple resistors and a capacitor or two in an adaptor box.
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Thanks for the heads-up Larryk. Every bit of information helps. I find that in the heat of the moment, when out in the field and something doesn't work as you expect, it's hard to think logically and rationally when trying to figure out which of the hundreds of things that affect settings needs to be tweaked or changed.?
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Re: SWR and PWR does not show lcd
So there is definitely some sort of defect here.?
But myself and many others don't experience it (some are seeing wildly swinging SWR), so it must be related to something else in your specific firmware/hardware or configuration, and Hans will likely need more information to be able to find/fix it.
A couple of things I would try, if you haven't already, which have a possibility of getting it to work:
- Just turn off the pwr/swr display option, exit the menu, then go back in and turn it on again.? This could potentially clear something that wasn't fully set properly - then see if it starts working.
- Do a 'factory reset' to bring all settings back to factory default, then turn on the pwr/swr display option and see if it works.? Of course this will undo any settings you have put in, so you may want to record them so you can easily put them back in.? Note that a firmware upgrade does not change any of the compatible settings, so there is some possibility that something set errantly in your eeprom before a firmware upgrade did not clear, and contributes to this problem.
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Other than that, I'm out of ideas for this strange behavior...
Stan KC7XE
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750 Hz Square Wave from #QMX Speaker while Transmitting
#qmx
#beacon
Does anyone else hear this constant 750 Hz square wave through the speaker while the QMX transmits a CW, FSKCW or WSPR beacon message only when the QMX is in USB or LSB mode?
While the QMX is in CW or DIGI modes the speaker remains silent during beacon transmissions . Watch my video at
QMX+ transceiver with Firmware 1_01_003
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Carol KP4MD
Michael N6QP
Brent DeWitt
Grant