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QMX+ shutdown problem
#qmx
#QMXplus
#shutdown
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My newest QMX+ kit Rev 3 arrived and was assembled exactly one week after ordering!
The diagnostics test page showed output power (0W) and SWR (random values). Everything else was OK. All sweep tests showed strange results. Yes, the dummy load was in place.
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So I decided to power off and check all solder joints again.
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The QMX was on the table without the enclosure and I did not get a good grip on it.
As I pressed the Vol button for power-off the QMX moved on the table and the long button press was interrupted, giving *two* long presses like keying Morse M.
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The display flashed abnormally showing some text and dimmed.
All happened so quickly that I did not see exactly what happened.
No smoke, no hot components.
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Now I can not power-on as the radio does not react to any button press. Nothing happens.
If jumpered for forced firmware update, no flash drive appears on the PC.
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This could be a firmware problem.?
Is it possible that the second long press of the Vol button started the power-on cycle while still powering off and writing data to the flash memory?
Clearly,?while performing power-off?and saving data into the flash memory,?the firmware should ignore the button press for power-on.
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73 Matti OH6BEX |
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Matti,
please read QMX QMX_plus Startup to find the switch on process. There you will find also some testpoints and values to check.
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How much supply current when pressing the left encoder? How much before and how much after?
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73 Ludwig |
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Ludwig, thanks again for reply! The ?QMX QMX_plus Startup is good advise.
I will try to measure some of those voltages and the currents as well.
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But still, I do not understand how all this happened.
A full working equipment stops working by just pressing some buttons of the user interface.
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The shutdown process did not show the shutdown message which is usually visible for about one second.
Instead, some message, possibly the shutdown message, flashed on the screen so quickly that I could not read it.
Then everything dark. Forever.
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How could this be caused by some hardware failure??
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73 Matti OH6BEX |
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On Fri, Feb 21, 2025 at 08:11 PM, Matti OH6BEX wrote:
Matti, hard to say without more information. Maybe after getting some results from your tests. ?
73 Ludwig |
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On Fri, Feb 21, 2025 at 07:11 PM, Matti OH6BEX wrote:
You applied pressure to the board. Maybe caused something to short circuit.
Even under the board, you had it on the bench unmounted.
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73 Alan G4ZFQ |
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Matti,
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? ?I was recently working on adjusting the toroid winding for power adjustment when my QMX+ display screen flickered quicky while handling it.? I look to see what may have caused it when I noticed my power connection was coming loose from the back of the unit.? ?After pushing the plug back into place, the QMX+ quickly powered off instantly.? ?
? After that the QMX would not power back on.? ?I tried everything under the sun to get the unit to boot back up.? ?NO GO.
?What I found was that my Zener diode D109 had shorted to ground.? ? I could test this theory by pressing the power on knob and holding my finger on either Q109 or Q111.? ?I am sorry but I forget which it was of the two transistors but anyway the transistor got instantly hot to the touch of my finger.? ?I then pulled one of the legs up on D109 to take the diode out of the circuit.? After doing so I attempted to power on the QMZX+ with 7v limited to 200ma.? ?What did you know, the QMX+ came back to life.? ??
? I repaired the unit by replacing the D109 Zener diode with a known good one.? ? (D109= Zener 3.6v 500mW)
? I think this may be the issue you may be chasing for why your unit is not responding to the power on button if I am following the event of how yours shut down.? ?
Also, I remember check that the resistance across VDD and Ground read something like 265 ohms.? ?It should be in the Kilo Ohms or higher.? ?You can begin there with checking with your ohm meter.? No power applied occurs.?
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P.S? ?
?I agree that for the no power out issue, double check that you added the jumper during your build.? ?Good Luck and hope this helps. |
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What firmware revision did you have when the rig failed like that?
What hardware revision?
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Latest firmware rev is 1-00-027, and seems to have reduced the occurrence of this sort of thing considerably.
If it still happens fairly often, then the power supplies may need to be looked at further.
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Jerry, KE7ER
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On Fri, Feb 21, 2025 at 02:04 PM, Kevin (KQ4DTX) wrote:
What I found was that my Zener diode D109 had shorted to ground.? ? |
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@ Jerry Gaffke,
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? Jerry, if your question was at me:? My QMX+ is Board V2 with firmware 1-00-027 when my occurrence happened less than a month ago.
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@ Mattie
?I see you checked your unit with 12.15 voltage applied.? ?Your results were no voltage at VDD and VCC when referenced with ground.? ?Please understand that these points are after transistor(s) that would kick in (switch on) after the Processer or Voltage Regulator circuit is satisfied with certain conditions.? ?Your unit is not meting those conditions.
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I suggested earlier that you check the Resistance with your ohm meter across VDD and Ground to see what the readings are.? This will let you/ us know if you have some damage part(s) on the 3.3v rail.? As I said earlier that mine had a reading around 260ish ohm (No Good) on that rail.? That told me that I needed to go down that rabbit hole looking for an issue there.? ?Mine ended up being that D109 was damaged and pulling the voltage to ground.? This didn't let the 3.3v power get to the proper voltage to power the circuits needing that power rail i.e., the brains of the unit, the processor.? ? If you choose to, please look at my earlier post and share your findings with what you get on checking the resistance across VDD and Ground. THIS IS WITH NO VOLTAGE APPLIED TO THE QMX+.? ?I just opened up my unit and confirmed that my resistance reading taking from JP105 VDD to ground is 2.54 K Ohms on the working unit.? Let us know the results.
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?If your results with the ohm reading is not above 1k ohms, I would then try testing the unit like I said in the earlier post.? ?Apply power (If you can put your unit on a regulated power supply with 7V, 250m amp limit setting).? Place a finger on the Q109 or Q111 (my version 2 QMX+ these were found on the bottom of the main board).? While holding down the Power Button, did the transistor get hot to the touch?? If the answer is yes than something is pulling too much current and not allowing the supply rail to get to 3.3 volts.? for me, the diode had shorted and cause the issue of pulling too much current to ground (D109).
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?I just trying to help so if you could post the results of your findings this could help the group understand what your next steps is/ are.
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73 KQ4DTX |
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I GIVE UP!
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Pressing the encoder the +12V pad showed 11,5V, Vdd 0,01V and Vcc 1,15 V.
But then, possibly the DMM probe shorted the Vcc and Vdd pads of JP105...
Every voltage is now zero, the encoder pressed or not.
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I really would like to see a robust QMX++ with linear regulators. So much trouble (me and many many others) with the SMPS'es.
Remember the KISS principle!
Saving some hundred mA may be relevant if running with alkaline batteries, but most of us are using AC powered chargers or massive lithium batteries.
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73 Matti OH6BEX |
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Matti,
Very unfortunate problems you are having. The voltages you measured with the button pressed show that you have something shorting in your QMX+, on both the Vcc and Vdd lines.? It is not easy to say exactly what is shorted without further measurements, but most commonly there are issues with connections and solder flakes.? Or something external.??
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And if you shorted your Vdd to Vcc while probing, if you didn't have a current limit of 250mA or less set on your power supply, you likely blew one of the protection diodes, probably D109.?
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But it is not accurate nor fair to blame these issues on the QMX+ v2 or v3 SMPS design. Shorting without a fuse or current limit would damage some component in almost any design, yes, even with linear regulators.
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Perhaps QMX+ should have been designed with a 250mA fuse on the Vdd line, then assembly or handing issues that cause shorts would blow the fuse rather than the protection diode - then instead of placing blame on a power supply design,? ?we would be looking for what is shorting and fix it.
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Also note that a double long-press of the power button shouldn't have caused any issue.? I have done that before without consequences. Similar with a very long press, which first powers down then powers back up.
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Stan KC7XE? |
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Hello Stan, Ludwig and Kevin,
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I did'nt give up!?I ordered a mid-band QMX kit and it works good (but produces little bit too much power (6+ W) on 60 and 15 meters).
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The QMX+ rev 3 does not start. With power button pressed, it takes 0.8 A current which slowly decreases to 0.5A.
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Vcc and Vdd are around 0.1 V.
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Testing diodes with a DMM: D108 shows 0.17V and 0.2V, D109 shows 0.11V and 0.12V.
meaning that both diodes are damaged. But as the diodes are in-circuit, these values are probably meaningless.
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Resistances:
Vdd - GND 184 ohm
Vcc - GND 2.4 kohm
Vdd - Vcc 9 kohm.
These were measured with the DMM black probe at GND or Vcc.?
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But when I swap the probes, the readings are
Vdd - GND 1.2 kohm
Vcc - GND 313 ohm
Vdd - Vcc 1 kohm.
Why?
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I also received some spare SMPS'es and installed those to the older QMX+ rev 1 which I broke by accidentally inserting faulty SPSM'es from another faulty QMX.
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Receiver works ok.
Diagnostics page is all OK except TX Voltage which is RED showing 10.4 volts (DC input is 12.2V)
Pressing "T" changes TX voltage to GREEN 9.8 volts, power 0.0W and random SWR values.
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Apparently something in the TX chain is destroyed.
I have no oscilloscope. Is there something that I could check with an ordinary DMM?
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73 Matti OH6BEX |
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On Fri, Apr 4, 2025 at 11:11 AM, Matti OH6BEX wrote:
0.8 A is to much. To start the controller you need Vdd at around 3 V. This voltage could be produced by IC101 but I guess there is a fault in the chain before. Pleas read QMX QMX_plus Startup to find this chain. A broken D109 is affecting Vdd. These values are not so bad and affected by the broken diodes. I guess you destroyed the PA and because of high current Q507 was following the PA in dead. Please don't transmit with a broken Q507 and read QMX QMX_plus PA problems, broken BS170 . Go to Terminal - Diagnostics (the controller will set a signal to switch off the PA voltage) and check voltage at D, G and S of Q507. If all values are nearly the same and high the Q507 should be broken. For more debugging check the Wiki page above. ?
73 Ludwig
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