开云体育

New QMX+ Calibration victim

Jonas Sanamon All Messages By This Member #144783 开云体育 Hi, 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? toggle quoted message Show quoted text 7 maj 2025 kl. 23:12 skrev Stan Dye via groups.io <standye@...>: ? On Wed, May 7, 2025 at 01:38 PM, Wiggle Pig wrote: It’s D503 and D504 These are placeholders for diodes that could be placed across the BS170 outputs, as was commonly done with QDX.? Hans included them in the design, but has not encouraged installing the diodes, which he believes are unnecessary for QMX.? They may suppress spikes, but they also add additional capacitance to the PA, which may affect it adversely in other ways.? There were many posts on this list regarding this topic a year or so ago. ? Stan KC7XE
Jonas Sanamon All Messages By This Member #144875 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

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