开云体育

ctrl + shift + ? for shortcuts
© 2025 开云体育
  1. QRPLabs
  2. Messages
Expanded Topics Messages Polls
Date
Re: #QMX holy smoke released again, C107 and D108 destroyed #qmx

 

Hans, I agree about the component failure scenario being unlikely.
I assume that the PWM signal is generated by a HW timer, you are not running a 166 kHz interrupt...
What if the software crash writes to the timer configuration registers and changes the function to a normal output?
Do you have a comment to making ghe? PWM signal AC-coupled?

73 de SM5EIE /Gunnar
Re: Stuck on my QMX build

 

Michael, not sure I understand - does the splash screen still show or did it only show one time?? What is the value of the current draw?? You can easily check to see if the 3 volt supply is working by using a ground on any of the connectors and probing any of the resistors on the control board.? With nothing pressed they should show ~3 volts.? This, of course, after power on button is pressed and released.
Re: Stuck on my QMX build

 

Colin i thought the same,
Hans posted (#103064)
  1. Initialize the Flash memory, reset peripherals, configure the system clock, configure the I/O pins
  2. Initialize the DMA (Direct Memory Access interface)?
  3. Initialize the ADC (Analog to Digital Converter) of the CPU; we use 10 channels for monitoring supply voltage, 3.3V, 5V and Bias buck converter outputs, Fwd/Rev power from the SWR bridge etc; all continuously read via the ADC and stored in memory using DMA
  4. SMPS (Switched Mode Power Supplies) initialization - this means the little plug-in buck converter boards.?
  5. DIsplay init - which initializes the LCD module, switches on the backlight (depending on if you configured that to be on in the configuration menu), and writes the Splash screen text (QMX, firmware version, QRP Labs 2023).?
  6. Blah blah loads and loads of other things - including eventually, the USB initialization...?
  7. Eventually, audio system initialization (the I2S 48ksps stereo ADC chip and corresponding stereo DAC chip
I seem to be at 5
Switches on the back light and writes the splash screen
the SMPS come before this so thats what puzzels me about what direction to go next
Re: #QMX holy smoke released again, C107 and D108 destroyed #qmx

 

Hello Gunnar

If the processor reboots, the PWM signal floats and is pulled low by a resistor. If the application firmware crashes for some reason?or hangs up - the interrupt processing?continues as it is in the highest priority interrupt. I don't know of any realistic scenario where the PWM signal can get stuck high, other than if there is a short somewhere.?

I'm quite hesitant to suspect that there is anything wrong with the capacitors, or with the design (which has a lot of failsafes built in, both in hardware and in firmware). To put it plainly - if we don't have any particular evidence for what caused a failure and are devoid of any explanation, I think it is a stretch too far to say that it is therefore probably a defective component. A failure of a component operated well inside its ratings is not very common.?

73 Hans G0UPL



On Sat, Aug 26, 2023 at 7:08?PM <Ugglekatten@...> wrote:
Rick,
I will repair the board with an axial lead zener of higher power rating and put a ceramic capacitor in place of C107.
Then I will fit a large electrolytic somewhere on the main board.
I will do a simulation of AC-coupling the PWM signal before deciding if I do that modification

73 de SM5EIE /Gunnar

2 Meter LPF

 

I got the 2M low pass filter and seems pretty straight forward, except one line...

" The middle coil should be a little longer (for lower inductance)."

What does longer mean? Wider spread on the coils? taller leads so it stands further/taller on the board?

Bob
KG5GTE
Re: #QMX holy smoke released again, C107 and D108 destroyed #qmx

 

Rick,
I will repair the board with an axial lead zener of higher power rating and put a ceramic capacitor in place of C107.
Then I will fit a large electrolytic somewhere on the main board.
I will do a simulation of AC-coupling the PWM signal before deciding if I do that modification

73 de SM5EIE /Gunnar
Re: Stuck on my QMX build

 

This sounds like it is hanging waiting for the switching regulator to spin up. It will pause the boot sequence till the voltages are correct and the switching regulator duty cycle is in the expected range. Then the current should drop to about 80ma. Hans has written about the a couple of times. Finding his description will give some places to probe.?
--
Colin - K6JTH?
Re: #QMX Spectrum analyzer data #qmx

 

Hi Chris,
thanks for sharing the spectrum images.

Although my comment is not useful for you here, I am glad about this publication, because it gives me the opportunity to compare my own measurements with the FA-NWT plus. The conditions are similar: 38 dB attenuator, but only 9 V voltage supply.

Here are my measurements for 80, 60 and 40 m:
Re: #QMX holy smoke released again, C107 and D108 destroyed #qmx

 

Daniel, I dont agree...
The resistance of L101 is 2 Ohm and with a good short circuit in C107 and D108 the voltage rise will be limited by the voltage drop over L101.
If the supply voltage is disconnected fast enough the damage should hopefully be limited to C107 and D108
To operate a 6.3V tantalum capacitor at 5V should not lead to a failure, unless the capacitor is faulty

73, Gunnar SM5EIE?
Re: #QMX holy smoke released again, C107 and D108 destroyed #qmx

 

Agree

It is definitely the case that Tantalum caps do that, surprisingly frequently and without much provocation
Unfortunately when they let go, like a Lithium battery there is a self fuelling exothermic reaction that has nothing to do with the applied power

Bad batch of caps ?

I would prefer to see an aluminium electrolytic to supply the uF and a parallel ceramic to handle the higher frequencies

Rick
Re: #QMX Spectrum analyzer data #qmx

 

Spectrums look fine to me, well within the legal requirements

Within your "QMX power and voltage tests" I se the TxV voltages are significantly less than the supply.? I see the same with mine. I think it may be the attenuator ahead of the processor's A/D.? Next time I have my QMX apart? I'll check the actual voltage.
Re: Stuck on my QMX build

 

Bruce
Rechecked the earths the on/off switch turns QCX on its is visible on the pc to load the software, it the lights up lcd and diplays clearly the splash screen. but nothing after power down and restart except for current draw.
Re: Stuck on my QMX build

 

Colin
Thanks for your help.? when the software loads the led lights up and the splash screen is clear to read. but nothing after reboot.
VFO signal generator frequency limits

 

When tuning the VFO signal generator does it limit the display to 200 MHz and 3.5 KHz?
If not what does it do when you goes past the chip limits?

Thanks
richard
Re: Stuck on my QMX build

 

Make sure you have the LCD contrast fully anti clockwise.?
--
Colin - K6JTH?
Re: Anybody running 6m on QDX?

GIUSEPPE
 

?Hello Jeff, I don't have a QDX for 6m, but I modified the QCX MINI to work on 6m, it has been transmitting 24h24 in WSPR mode for more than a year, it has 3W output, I think u.? QDX can be modified by replacing the capacitors and rewinding the toroids involved, I don't know if it could be good for FT8, but in CW and WSPR mine is fine, I think I'm the first and only one in Italy to ever do this edit.? I didn't get any help because everyone scolded him because it wouldn't go well, I was stubborn, I tried and I succeeded.? Now I don't know the QDX scheme, I can't advise you to try it, it would be at your own risk, I just sacrificed a qcx mini only for this band without knowing of my success and I'm happy about it.? It currently broadcasts with a 1.5m long car antenna, on you will find all the stations that have listened to me.? I hope you can make it. good luck.? 73. I forgot, on youtube I have 2 videos showing the qcx mini being broadcast on 6 mt wspr and on there are photos.? Hello iu8eun Giuseppe

Giuseppe iu8eun

Il Sab 26 Ago 2023, 15:57 Jeff <jeff.ve3cw@...> ha scritto:
Hi All.

I have recently sold the rig I used to have running 6m FT8 to monitor for openings.? Was wondering if there is anybody that has a QDX set-up and running on 6m?? Would love to connect to discuss mods necessary to get it done if you have one up and running.

Thanks
73/72
--
Jeff Hetherington
VE3CW / VA3JFF
Anybody running 6m on QDX?

 

Hi All.

I have recently sold the rig I used to have running 6m FT8 to monitor for openings.? Was wondering if there is anybody that has a QDX set-up and running on 6m?? Would love to connect to discuss mods necessary to get it done if you have one up and running.

Thanks
73/72
--
Jeff Hetherington
VE3CW / VA3JFF
Re: Stuck on my QMX build

 

Michael,
If the buttons and the right encoder don't respond , check the ground connection to the control board, the upper left pin ( or either of the button contacts near the top edge).? Also be sure the mating ground pin on the main board is solid .? As noted in the manual, the six layer board grounds take a lot of heat for a good connection.
Good luck!
73 KG8IW?
Re: #QMX holy smoke released again, C107 and D108 destroyed #qmx

 

Gunnar,?
If this was a high voltage HW/SW glitch, you should ?have fried the whole 5 V bus, or at least IC402/403. My similar failure occurred at 13+ V but did not take out the 5 V bus, so I don't think 13+ V ever got past the SMPS, although I can't prove that.?
--
73, Dan? NM3A
#QMX Spectrum analyzer data #qmx

 

I've obtained some spectrum analyser images of the output from my QMX running at 12.5V.? This is in preparation for fitting Zeners so we can check before and after.? This is the before.

Is this the information that we need to check the performance? I'm not an expert at this and would appreciate knowing if more data is needed.? I don't intend to keep soldering and unsoldering Zeners.

I'm running the QMX into a home made 38.7 dB 8W 50 ohm attenuator (4 x 51R 2W SMDs arranged 2x2, then a 2k2, then 2x100R SMDs).? I've a 10W 20dB attenuator coming.
34041 - 34060 of 141041