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Re: QMX+ no power output, low SMPS bias current
One of my bnc adapters to my dummy load recently failed,? too, and was very flaky.? Not an uncommon problem.
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For the power output, do LPF scans and see how they are responding.? The efficiency of the T501 windings can also affect power out on the higher bands.?
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Stan KC7XE? |
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Re: QMX+ with WA3TFS amplifier
Jim:
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Excellent work and yes, surgery went well but there will be some rehab involved - I¡¯m really sore right now. Right now, I can¡¯t get up the stairs where the shack/bench is located. But, it¡¯ll still be there. Your solution will work great for the QMX with wired PTT. But what if I decide to use say, a FT-818 that might use RF detection ? I might need a closure of that circuit when there is no TRS plug.
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Just food for thought ¡ which right now, I admit, mine isn¡¯t very clear right now. ?
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73, Jamie
WB4YDL |
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Re: QMX+ no power output, low SMPS bias current
I rewound T507 and got pretty much the same results, until I checked the BNC connector on my dummy load, and discovered it had been damaged and wasn't giving a consistent connection.? I pulled out my bigger dummy load and put a BNC adapter on it, and was able to get the following values:
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So it seems like I'm almost there.? I just need to figure out why my power is so low on 6, 10, 12, 15, 20 and maybe 40 meters. |
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QDX-M 80m
#80m
Hi All,
I have a plan to build a QDX-M for 80 metre FSQ activities. The QDX-M appears to be ideal for this with it's clever non SSB method of producing the tones required. However, the web page shop only lists 10,11,12 metre bands at the moment. After looking at the circuits for the QDX and QDX-M the changes for 80 metres would seem to be: 1. Use the low pass filter design for 80 m from the QDX. i.e change the inductors and capacitors in the QDX-M to be the same as the 80 m filter in the QDX. 2. Change the inductor in the QDX-M (L12) so that it resonates with the 56 pF capacitor at 3.6 MHz. 3. It looks like L14 remains the same for all bands. So my question is: Has anyone done this and are there any steps I've missed, and can I buy a QDX-M kit with all the appropriate toroids, inductors, and capacitors? I'd like to buy one QDX-M for 80 metres and one extra set of components to change the unbuilt 10 metre QDX-M I have to 80 metres. Apologies for the long and involved post. Best Regards Richard Katsch VK2EIK |
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Stan and Ludwig:
1)? Some conflicting information to clarify/resolve: in one place you say "ADC_3V3 measures 6.6V" and another you say you measure 3.3V at ADC_3V3 (which corresponds with the 6.6V seen in the diag screen).? But you also say that Q111 source is cleanly at 10.6V.?? This doesn't quite add up: if Q111 source is at 10.6V, then ADC_3V3 must be at 5.3V (not 6.6 or 3.3), because of the resistor divider of R110 and R112.? So something is still wrong with this measurement picture, or something is interfering.
Ah, yes, confusing. Actual measured is 3.3v at ADC 3V3. Which as you mentioned Indicates an actual VDD voltage of 6.6. But as I noticed also, the diag screen says 5.3. So no, actuals and calculated values do not add up. I also thought that 10.6 should show up as 5.3 at ADC 3V3. Maybe it is confused by the VDD actual measured being 2.97 (sourced by IC101) and ADC 3V3 being 3.3 measured indicating a VDD of 6.6v. Hopefully I didn't make it more confusing. Suffice to say. I agree...
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2) And since the voltage at Q109 Drain is not going down to 0V, it is not getting fully turned off, or it could be damaged.? I would check the voltage waveform at Q109 gate. ?R107/Q113 should be pulling the Q109 gate up to very near its source voltage when PWM_3V3 is low, which should turn off Q109. ?If this is happening, then Q109 is probably broken.? If the gate voltage is not getting that high (which I suspect is the case) then another of the PWM components isn't doing its job.? Check to make sure PWM_3V3 looks like a good pulse wave from 0V to almost 3V, and check the Q107 drain and Q113 emitter voltage waveforms to diagnose where the problem is.?
Right. On the Schem. I show the waveform at Q109 gate / Q113s emitter. It is ramping up to 12v and back all the way down to 0v, hold for a bit and repeating.
The waveform on PWM 3V3 is perfect, Q107 drain is a clean square/rectangle wave duty cycle matching the gate.
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Ludwig
Randy, something is strange. Early you wrote VDD is produced by the linear regulator. LIN_REG_EN must show some volts to connect IC101 to "+12V" via Q102. Your schematic shows 0V at LIN_REG_EN. Appropriate Diagnostics show the status SMPS. This should switch off IC101. So there maybe a (helpful) failure.
Yes. Because I lifted Q111 and D109 it has to be coming from the linear regulator. Why it is on when LIN_REG_EN is at 0v I do not know. Maybe Q102 is shorted.
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LIN_REG_EN at 0V would also switch off Q110 and R114. R114 is an artificial load to operate the SMPS without a real load. It's hard to adjust a SMPS with (nearly) no load. Maybe this is the reason for the too high voltage at D of Q109.
That is what I suspected. Drain floating in the breeze.
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A not well working Q113 may cause a similar effect. Please check the oscillogram at B of Q113. It should show rectangle from around 0V up to "+12V". The voltage at E of Q113 should follow but with around 0.7V at low and "+12V"-0.5V at high.
Nice square (rectangle) wave on the base of Q113. The wave form on the emitter is equivalent to what I see on the 5v circuit. It is shown on my schematic. Different duty cycle.
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Thanks for all of the input. I have a full complement of replacement components arriving on Thursday. We will soon find out who the culprit is.
My money is on D109 at a minimum since it won't power up at all when it is in-circuit.?
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Randy, N4OPI |
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I did not go mobile, but rather made a recording of the audio on my ICOM transceiver. These were my final settings after trying various settings on my QMX with the Heil Pro 7 (IC)headset. I worked a couple of POTA stations who said my audio was clear, just weak. I left some heading words out but I think you will get the idea. Hope this is helpful.
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EQ
?On
?Global -17
?300
?+2
?.5
?3000
?0
?.9
?
AGC
?On
?10
?10
?2
?
RX filter
?2500
?
TX filter
?2700
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Mic gain
?63
Comp
?3
?
Noise Red
?On
?
Noise Gate
?On
?Thresh 50
?99
?Att 10
?
Vox
?On
?Thresh 35
?Hold 6
?
Drive 900
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CESSB On
?
Phase PD On
?
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Re: CW Practice / Rag Chew
I wouldn't describe a K of 5 as good. A figure of 1 or 2 is much better. The lower bands eg 40m may be very difficult to use at a K of 5. Digital will stand the best chance of getting through on these bands. The SFI is an indication of how well you can get DX as a higher number helps the signal to skip multiple times especially on the higher bands eg 10m. The A figure you can ignore as it is showing what's happened in the past. The SSN figure is a measure of sun spots and closely follows the SFI figure.
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The above is a brief over-simplification but might help.? |
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Very good Mel!
I think a mic preamp perhaps on a daughter board with special consideration to low noise components, good equalization, layout and filters, and a low impedance output to feed the QMX A/D converter would be an excellent addition to the QMX. Depending on the dynamic range of the A/D converter and a higher input signal, one might not need the spur removal with the internal mic and second A/D converter. ?
I have some small mic preamp boards, and designed a discrete one for a dynamic mic I had. I will ?have to give it a try if the Pro 7 doesn¡¯t work well. |
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The headset has a electret mic. I didn't measure the resistance. It sounded perfectly adequate when I used it on my pc.
Hower, the output from the mic seems too low using it with my QMX+.
I did try two other electret capsules I had in my junk box, they were marginal improvement over the headset mic.
The headset works great with the mic preamp, however.?
The mic gain is set to 35 and compression set to 3, produces good results on my QMX. |
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Mel, was the gaming headset mic an electret element, or another type like dynamic or crystal elememt? What does its resistance measure?
Gaming headsets are known to be poor quality in general. In my mobile IC-7100, I used a headset with mic but from a well known reputable company and with an electret mic. It worked great for the 7100. |
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QMX+ Died on the Operating Table?
I started having problems with my QMX+ ver 1 after the SSB calibration.? I ended up replacing the BS170s in the final amp which got me back to full power.? However, I noticed that the power was not reducing in SWR test mode like it should.? I determined that the power modulation transistor Q507 had probably failed.
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I replaced Q507 with a new transistor, but the QMX+ did not survive the operation.? I am now unable to get the QMX+ to power up.? I suspect that I damaged the board when I removed the old transistor and now have a short to ground on the board under the transistor.
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Is there hope of bringing this QMX+ back to life, or is it time for a new main board?
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--
Steve KA0SM |
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FT8CN Getting it to Work!
I installed FT8CN to an Android phone but found it sometimes transmitted and often did not.?
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Then I discovered there is a magic button on the screen which turns on transmission! It is in the top right of the Calling screen and looks like a loudspeaker. You need to click on this until it turns red as shown on the screen shot. I also discovered by repeatedly clicking this button it changes the "Sequential" setting between 0 and 1 which changes whether it transmits in the first or second time slot.
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I have read the English manual but don't remember seeing these controls.?
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The settings are QDX rig selected which works with my QMX and CAT control. Everything else is default. Phone is a Google Pixel 9a.
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Ok, good new information always helps.? Looks like the processor is indeed able to measure the voltage at ADC_3V3, but I am quite confused about why the processor would be maxing out its 3V duty cycle at 27% when the voltage is higher than 3V - it seems that it should be reducing the duty cycle to reduce the voltage -- but the processor is probably confused, since its own VDD is at 2.97V (from the linear regulator), and isn't changing.? Because you have the drain of Q111 lifted, VDD and the ADC_3V3 voltages don't track.
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The data you present gives two other issues to resolve, before restoring the drain of Q111:
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1)? Some conflicting information to clarify/resolve: in one place you say "ADC_3V3 measures 6.6V" and another you say you measure 3.3V at ADC_3V3 (which corresponds with the 6.6V seen in the diag screen).? But you also say that Q111 source is cleanly at 10.6V.?? This doesn't quite add up: if Q111 source is at 10.6V, then ADC_3V3 must be at 5.3V (not 6.6 or 3.3), because of the resistor divider of R110 and R112.? So something is still wrong with this measurement picture, or something is interfering.
?
2) And since the voltage at Q109 Drain is not going down to 0V, it is not getting fully turned off, or it could be damaged.? I would check the voltage waveform at Q109 gate. ?R107/Q113 should be pulling the Q109 gate up to very near its source voltage when PWM_3V3 is low, which should turn off Q109. ?If this is happening, then Q109 is probably broken.? If the gate voltage is not getting that high (which I suspect is the case) then another of the PWM components isn't doing its job.? Check to make sure PWM_3V3 looks like a good pulse wave from 0V to almost 3V, and check the Q107 drain and Q113 emitter voltage waveforms to diagnose where the problem is.?
? |
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Randy, something is strange. Early you wrote VDD is produced by the linear regulator. LIN_REG_EN must show some volts to connect IC101 to "+12V" via Q102. Your schematic shows 0V at LIN_REG_EN. Appropriate Diagnostics show the status SMPS. This should switch off IC101. So there maybe a (helpful) failure.
?
LIN_REG_EN at 0V would also switch off Q110 and R114. R114 is an artificial load to operate the SMPS without a real load. It's hard to adjust a SMPS with (nearly) no load. Maybe this is the reason for the to high voltage at D of Q109.
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A not well working Q113 may cause a similar effect. Please check the oscillogram at B of Q113. It should show rectangle from around 0V up to "+12V". The voltage at E of Q113 should follow but with around 0.7V at low and "+12V"-0.5V at high.
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73 Ludwig |
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John Laidler
Bruce Akhurst
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