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New QMX+ Calibration victim
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On Fri, May 9, 2025 at 07:57 PM, Jonas Sanamon wrote:
as it shows the 5v to be 5.6v at the same time as the SMPS duty cycle is 0%.?Hi Jonas, I guess the zener D108 limits VCC to 5.6 V.
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Yes. PWM (pulse width modulation) is an output and ADC_5V an input. If VCC is to high and PWM from the controller is 0 I see two possible reason:
The problem was caused by a calibration, so when the QMX was transmitting. I see one related "connection" between "+12V" and VCC. It's from the PA voltage via the BS170 and IC503. I suggest to cut the PA voltage from the BS170 (lift one leg of L502) and test, check the Diagnostics screen. If VCC and Duty cycle are ok (or better), the PA is fishy.
But if you see the known problem, remove Q108 and check diagnostics screen. Duty cycle should be equal to Duty max and VCC at low level. But if VCC would be high (5.6V) search for the point where VCC is connected to "+12V".
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After knowing about your results we will discuss the next steps.
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73 Ludwig
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Continuing my own thread :-) Troubleshooting of my SSB calibration casualty QMX+ continues. After lowering the external PSU voltage limit a little?bit furher?to 7v?and lowering the current limit to 250mA I dared testing to allow the QMX+ to be powered on long enough to access the built-in diagnostics page. As suspected it shows that the 5v regulation doesn't work as it shows the 5v to be 5.6v at the same time as the SMPS duty cycle is 0%.? The sensing part seems to work though as it appears to try to lower the voltage by using low duty cycle.? Unfortunately as I'm looking at the schematic for the QMX+ PSU, I don't understand how it's supposed to work. Is there a description of this available somewhere? For example, which signals are inputs and which are outputs?? I assume the "5V PWM" is an input from the CPU. If this is low, then Q106 does not conduct, leading to Q108 also not conducting?? Best Regards Jonas - SM4VEY |
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Update:
Visual inspection showed that Q108 was broken as it had its case cracked. Cannibalized another unbuilt QMX+ board and replaced it. Measured and found D108 shorted and replaced it as well. Now with PSU set to 7.5v and current protection set to 350mA I dared to test to start the QMX again. Now it starts up but it¡¯s quickly visible that some voltages are not right as the contrast is way to high on the LCD. So I quickly unplugged the power. (For a brief part of a second the display shows the startup information correctly before turning black probably as the 5v? rises to too high. Maybe the SMPS regulation isn¡¯t working) Open and greatful for further ideas on how to continue troubleshooting ? Jonas - SM4VEY |
¿ªÔÆÌåÓýHi,I¡¯ve had my QMX+ for a number of months and had tested the then beta now regular SSB firmware with good results except pretty low output power in SSB.? As I had never gotten around to fine tune the LPFs when building it I decided this was the logical next thing. So I fiddled with spreading and compressing turns on the toroids and managed to get all bands to between 4 and 5w output for CW except 160m that was already at 6w.? Running 12.0v input and build for 12v Being happy with results I then first tested resetting to factory defaults, and then tested SSB output power. ?Still max 2-2.5w according to the Bird.? I then decided to run the SSB calibration again.? Worked fine til perhaps 12m or 10m phase. I then heard some terrible noise from the speaker and saw the QMX crashing with all blocks in the display and turning itself off.? I tried powering on again, but won¡¯t start now. Just blank display and current protection on PSU kicks in due to over current.? I suspect maybe finals are fried with internal short as result? Jonas? 7 maj 2025 kl. 23:12 skrev Stan Dye via groups.io <standye@...>:
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