Re: QMX high current consumption when input voltage above 10 Volt
John,
I accept your analysis, thank you!
What finally convinced me was that if I put a pull-down resistor of 2.2kOhm in parallell to R502 the drain voltage of Q501 change is only about 10mV up.
It is steady at 7.38V when the source voltage of Q502 is 8.97V.
It should be the same, so the conclusion is that Q501 is leaking!
I will replace it.
Thank you very much for your help
73 de SM5EIE / Gunnar
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Re: Fix For QCX+ volume pot?
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#qmx - watch out for DC jack clearance
#qmx
I had noticed some intermittent glitchiness in my QMX, particularly when holding it in-hand (vs sitting on the bench) - it would sometimes change between CW and digi randomly, or worse it would just completely shut off or show the "black screen" on the LCD. I determined that this was something mechanical because some tapping around the DC jack / volume encoder area would sometimes reproduce it.
I unscrewed everything and noticed that the left encoder is *very* close to the raw +12V from the exposed back of the DC inlet... enough to where some manipulation of the DC jack or tapping the encoder would cause it to short to the metal body of the encoder. This can be exacerbated by how you clipped the lugs off -- in my case I had bent them out to make them easier to snip off so there was an infinitesimally small portion that was sticking out beyond the case. It didn't appear that the encoder body is electrically connected to anything (even GND) so I'm not quite sure what is happening... either way I just put some Kapton tape over the back of the DC jack and the problem went away.
Just thought others might encounter this. It depends largely on the mechanical tolerances but I figured it's better safe than sorry to keep that 12V away from where it shouldn't be.
73
Andrew KI7FXL
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Re: QMX high current consumption when input voltage above 10 Volt
Gunnar, Either that means your firmware has been corrupted or this is extant and epidemic.
Re-flash your firmware if you believe the first to be true. I can't imagine the second to be true.
My vote remains with Q501 being damaged. I have seen this behavior before on another fellow's QDX. Replacing the transistor restored proper function of the bias generator.
A MOSFET with gate oxide damage may still function to some degree, depending on the level of damage and the strength of the driving circuit. That may be why things seem to be OK in transmit.
Also, the dynamic drive capability of a microcontroller output is not necessarily the same as its static current sinking ability.
Look again at the big difference in measurements you made at Q502 v. Q501. I think changing Q501 is in order.
JZ KJ4A?
John,
since the microcontroller can get the PWM voltage down to 0 during transmit, it looks more as if the microcontroller changes the port to an input port for some reason.
I attach an image from the oscilloscope showing the beginning of a transmission
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Re: QMX Digi not decoding & off freq.
Follow up:
after turning off QMX and restarting, working fine 005 f/w.?
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73, Dan? NM3A
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QMX Digi not decoding & off freq.
When I first got my QMX, I made a few FT8 contacts on 40m & 20m with no problems. I have since concentrated on CW. Now that that's working pretty well, I have gone back to FT8.
I noticed some weird things. (QMX F/W 005, QDX F/W 09; WSJT-X 2.5.4 for QDX & QMX)
- No signals at 7.074 or 14.074 in digi mode. Changing frequency up 3kHz brings up usual signals on graph. However, rare decodes! Not able to have QSO.
QMX was on LSB. Changing to USB showed same symptoms. Tried changing CW-R to OFF. Turned off CW decode. Turned off S-Mtr & Batt icon. All other settings at default. No change with any change in settings. Went back to 003, then 001 f/w with no change.
Putting QDX online showed normal functioning of FT8. Full decodes and easy QSOs.
Any one else notice this? Any ideas?
Dan
de NM3A at mail dot com
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73, Dan? NM3A
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Re: QMX high current consumption when input voltage above 10 Volt
John,
since the microcontroller can get the PWM voltage down to 0 during transmit, it looks more as if the microcontroller changes the port to an input port for some reason.
I attach an image from the oscilloscope showing the beginning of a transmission
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Re: QMX USB socket not soldered?
#qmx
I have just finished restoring a Yaesu FT902DM and some of the soldering on the internal boards looks a lot worse than that.
73s Ted
2E0THH
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the QCX+ 10 died during the field day. It was suddenly constantly transmitting.? No Idea what happened but later I noticed? that one line between the Key and the Atmega was having a low resistance. I swapped the Atmega with the one from my defective QCX 20 m and that was solved but otherwise the QCX was silent.
Once again DK3UM Hajo saved me and did the repair. The BS 170 of the finals were dead as well as Q5 and Q6 and IC 1.? I am still to test the QCX but? as he had it Hajo measured 0,3?V at 10 db SN which I think is pretty sensitive for 28 Mhz.
So maybe see you during the next challenge with it.
Martin
DK3UW
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Re: QMX high current consumption when input voltage above 10 Volt
Oh, I see you have already done that! Your numbers do suggest a failed transistor.
JZ
On Tue, Jul 25, 2023, 10:26 AM John Zbrozek < jdzbrozek@...> wrote: Gunnar,
Your observation of 1 volt at the PWM input is strongly suggestive of a gate to drain short in Q501. The resulting current flow into the microcontroller pin could overwhelm its ability to hold a down level.
Check that Q501 for unusual gate to drain resistance. With power off you should see numbers in the vicinity of 100K ohms. Much less would indicate a gate oxide failure in Q501.
JZ
Thank you all for your answers, I will try to answer all your questions in the order received:
Peter G3SPL, well I noted that the minimum power consumption occurred at 9.2V.
If everything was OK it would get lower at higher voltage, but not.
This is an indication that something is not right
John Z and Alan, you came to the same conclusion as I did
All measurements are taken with a supply voltage of 9.0V
John Z:
both sides of R505 show 0.749V DC, no AC signal superimposed
PWM signal on the gate of Q501 is only present during transmit, amplitude 3.3V, goes to 0V between pulses
The strange thing is that in receive it does not rest at 0, it rests at 1V. Looks like the PWM output is changed to an input at receive
Q502: resistance gate to source 700kOhm, gate to drain 740 kOhm
Q501: resistance gate to source 10/7.3? kOhm, gate to drain 12/28 kOhm The first value with the plus tip ov the DVM connected to the gate, the second with the minus tip
My own conclusion: the signal on the gate of Q501 should be at 0V in receive... maybe i should try with a 10kOhm pulldown resistor in parallell with R502??
br SM5EIE / Gunnar
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Re: QMX high current consumption when input voltage above 10 Volt
Gunnar,
Your observation of 1 volt at the PWM input is strongly suggestive of a gate to drain short in Q501. The resulting current flow into the microcontroller pin could overwhelm its ability to hold a down level.
Check that Q501 for unusual gate to drain resistance. With power off you should see numbers in the vicinity of 100K ohms. Much less would indicate a gate oxide failure in Q501.
JZ
Thank you all for your answers, I will try to answer all your questions in the order received:
Peter G3SPL, well I noted that the minimum power consumption occurred at 9.2V.
If everything was OK it would get lower at higher voltage, but not.
This is an indication that something is not right
John Z and Alan, you came to the same conclusion as I did
All measurements are taken with a supply voltage of 9.0V
John Z:
both sides of R505 show 0.749V DC, no AC signal superimposed
PWM signal on the gate of Q501 is only present during transmit, amplitude 3.3V, goes to 0V between pulses
The strange thing is that in receive it does not rest at 0, it rests at 1V. Looks like the PWM output is changed to an input at receive
Q502: resistance gate to source 700kOhm, gate to drain 740 kOhm
Q501: resistance gate to source 10/7.3? kOhm, gate to drain 12/28 kOhm The first value with the plus tip ov the DVM connected to the gate, the second with the minus tip
My own conclusion: the signal on the gate of Q501 should be at 0V in receive... maybe i should try with a 10kOhm pulldown resistor in parallell with R502??
br SM5EIE / Gunnar
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Re: QMX high current consumption when input voltage above 10 Volt
Thank you all for your answers, I will try to answer all your questions in the order received:
Peter G3SPL, well I noted that the minimum power consumption occurred at 9.2V.
If everything was OK it would get lower at higher voltage, but not.
This is an indication that something is not right
John Z and Alan, you came to the same conclusion as I did
All measurements are taken with a supply voltage of 9.0V
John Z:
both sides of R505 show 0.749V DC, no AC signal superimposed
PWM signal on the gate of Q501 is only present during transmit, amplitude 3.3V, goes to 0V between pulses
The strange thing is that in receive it does not rest at 0, it rests at 1V. Looks like the PWM output is changed to an input at receive
Q502: resistance gate to source 700kOhm, gate to drain 740 kOhm
Q501: resistance gate to source 10/7.3? kOhm, gate to drain 12/28 kOhm The first value with the plus tip ov the DVM connected to the gate, the second with the minus tip
My own conclusion: the signal on the gate of Q501 should be at 0V in receive... maybe i should try with a 10kOhm pulldown resistor in parallell with R502??
br SM5EIE / Gunnar
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Re: #qmx receiver optimization - what are folks getting for image rejection?
#qmx
Thanks, Hans. Like I said, this is mostly my own personal neurosis since qualitatively the radio is working great... I'm just striving to factor out my "style" and luck as much as humanly possible. I probably shouldn't worry about it so much. I'll take "basically built it correctly" though!
As a silly aside, you should implement old-school DEC ReGIS terminal graphics to make those sweep plots look real pretty... I think xterm on Linux will still grok it today. Or at least support dumping the data in CSV on-screen so us number nerds can plot it separately.
Thanks and 73,
Andrew KI7FXL
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Re: Another QDX went up in smoke
Well, not just a component?
We summer in Maine and when closing up in the fall place the toaster in the microwave to keep critters and dust out.
This year I opened the place up myself ahead of my XYL and the clock was flashing so proceeded to set it and accidentally hit the on button. ?Only a couple of seconds went by but the toaster was indeed toasted (;-(
Duh,
John
We travel to Maine _._,_._,_
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My Rev 3 is working beautifully with no mods.?
73
Dick
W4PID
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Well, I feel kind of dumb.? I had the power setting set to full power in WSJTX/JTDX, but the output at the system level (through the pulse audio control) was only about 50%.? Setting that to 100% resulted in a station in Germany calling me - not bad for 4 watts into an EFHW!
As for the CAT settings, it should be TS-440S in fldigi and WSJTX, but TS-450S in JTDX.? I don't know why, I only know that using TS-440S in JTDX fails to transmit (the radio goes into transmit mode and then drops out after about 2 seconds).
Thanks for all the kind suggestions!
73,
Mike, KL7MJ
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Re: QDX on 30m this morning
Tnx QSO, WB4EVH
72,
Bill, N4QA
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Re: QMX high current consumption when input voltage above 10 Volt
For completeness, check Q501 for shorts as well.? JZ
On Tue, Jul 25, 2023, 7:56 AM John Zbrozek < jdzbrozek@...> wrote: Gunnar, one more thing... With power off check the resistance from Q502 gate to drain and gate to source. If a short to gate has developed both Q502 and Q501 will exhibit elevated temperatures.
JZ
On Tue, Jul 25, 2023, 7:35 AM John Zbrozek < jdzbrozek@...> wrote: Gunnar,
It is as if the feedback loop that controls the bias buck converter is not working.
Check at both sides of R505 to make sure the ADC is getting a converter output sense signal. Check at the gate of Q501 to make sure a controlling PWM signal is present.
JZ KJ4A?
On Tue, Jul 25, 2023, 7:05 AM John Zbrozek < jdzbrozek@...> wrote: Peter,
Gunnar should be able to receive at 12v without drawing excessive current. Had he wired for 12v operation, that would be mandatory. I believe he is correct in his assessment that something is amiss.
JZ KJ4A?
On Tue, Jul 25, 2023, 6:37 AM G3SPL < leepd60@...> wrote: On Mon, Jul 24, 2023 at 10:58 PM, <Ugglekatten@...> wrote:
My newly built QMX has a strange behaviour...
When supply voltage is 9V current consumption on receive is 110mA on tranmit 1.27A
Output power is fine on all bands.
I can hear signals on all bands
But when i raise supply voltage to 10.5V the current consumtion goes to 220mA, at 11V it goes to 300mAn (always in receive)
Hi Gunnar.? You say that the QMX works fine with good receive and output power when operating with 9V.? Why are you trying to run a higher voltage supply?
?
--
Peter Lee
G3SPL
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Re: Here's what QSOs look like from the W4MAI ( SK 2006 ) Memorial Sun room monitoring station.
Tnx agn, WB4EVH.
72,
Bill, N4QA
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Re: QMX high current consumption when input voltage above 10 Volt
Gunnar, one more thing... With power off check the resistance from Q502 gate to drain and gate to source. If a short to gate has developed both Q502 and Q501 will exhibit elevated temperatures.
JZ
On Tue, Jul 25, 2023, 7:35 AM John Zbrozek < jdzbrozek@...> wrote: Gunnar,
It is as if the feedback loop that controls the bias buck converter is not working.
Check at both sides of R505 to make sure the ADC is getting a converter output sense signal. Check at the gate of Q501 to make sure a controlling PWM signal is present.
JZ KJ4A?
On Tue, Jul 25, 2023, 7:05 AM John Zbrozek < jdzbrozek@...> wrote: Peter,
Gunnar should be able to receive at 12v without drawing excessive current. Had he wired for 12v operation, that would be mandatory. I believe he is correct in his assessment that something is amiss.
JZ KJ4A?
On Tue, Jul 25, 2023, 6:37 AM G3SPL < leepd60@...> wrote: On Mon, Jul 24, 2023 at 10:58 PM, <Ugglekatten@...> wrote:
My newly built QMX has a strange behaviour...
When supply voltage is 9V current consumption on receive is 110mA on tranmit 1.27A
Output power is fine on all bands.
I can hear signals on all bands
But when i raise supply voltage to 10.5V the current consumtion goes to 220mA, at 11V it goes to 300mAn (always in receive)
Hi Gunnar.? You say that the QMX works fine with good receive and output power when operating with 9V.? Why are you trying to run a higher voltage supply?
?
--
Peter Lee
G3SPL
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Andrew KI7FXL
Ted 2E0THH
KK4ITX John
Richard Hattaway