I can vouch for locking screw-ons of 2.5 mm jacks and plugs.
Switchcraft jacks are not TOO pricey but lordy their plugs cost a bunch.
Found some decent 4 pack screw together 2.5mm jack/plug combos on Amazon for about $10 per set. Enter this in the Amazon Search box:
Ruiwaer 4Sets 5.5mm x 2.5mm Male DC Power Plug Connector with Screw Lock Female Panel Socket Mount Adapter Soldering Power Jack Connector and Screw Lock Female Panel Socket Mount AdapterRuiwaer 4Sets 5.5mm x 2.5mm Male DC Power Plug Connector with Screw Lock Female Panel Sockets?
The jacks are panel mounts so had to fiddle those into place and run insulated, short jumpers to the existing barrel connector pads (after removing the OEMs). Also had to enlarge the through holes in the end panels.?
And have to remember to remove the holding nut before removing the applicable end panels on my QMX HB and QDX LB units. I'll be retro fitting my QMX+ soon too.?
I soldered the plugs onto shortish, flexible wire runs with 12 and 9 volt USB C trigger adapters hard wired on the other ends. Pic attached.?
I put BIG '9' or '12'? labels on the cases of the Q's to remind me which adapter to use, but generally just leave the correct power-in cables screwed onto? the Q's.?
Reasonable bumping or jiggling has not caused any? glitches (or worse) so far.?
GREG KI4NVX?
Yahoo Mail: Search, Organize, Conquer
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On Wed, Jan 22, 2025 at 12:11 PM, Jerry Gaffke via groups.io
<jgaffke@...> wrote:
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Are these blown power supplies still happening with the latest version of firmware for the QMX?
We haven't been seeing many reports of this lately in the forum, I was hoping it was mostly resolved.
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I think a very brief interruption of power could be causing the problem, perhaps a disconnect of 100 microseconds or less.
The 5v rail falls, and if the processor inspects the ADC_5V input from the SMPS at just the right time when there is still
enough power to keep the processor going, it will bump up the PWM_5V duty cycle and the current through the inductor
quickly ramps up to far more than the nominal 100 ma that is needed before the next time the processor inspects
the ADC input some 1000 microseconds later.? (Likewise for the 3.3v rail with ADC_3V3 and PWM_3V3).
Since this depends on exactly when the processor inspects the ADC input, it won't happen very often.
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All conjecture on my part, would be worth looking into further if this is happening with current firmware.
Hard to model without knowing exactly what the software is doing to control the PWM signals.
For example, if the software sees that the 12v input has suddenly gone low, it could immediately inhibit
any increase in the PWM duty cycle.? I believe current firmware does something like that, but there may?
be a digital filter between the inspection of the 12v rail and where the PWM duty cycle is calculated.
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Using a 2.5mm plug in the 2.1mm jack in back of the QMX could definitely make for an intermittent connection there.
And if both truly are 2.1mm, there might still be an issue if these are budget parts with wide dimensional tolerances
and nothing springy in the metal to maintain connection.
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Moving up to a similar barrel connector from Switchcraft that has a screw lock to keep the plug
securely attached may fix this, but that might be $10 instead of $0.10.
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Moving to an SMPS IC would allow the supply rail to be inspected at a rate 1000 times faster
and should solve the issue while using reasonably small caps and coils and no increase in cost.
But it is not yet clear to me that this is still a problem worth solving.
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Jerry, KE7ER
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On Wed, Jan 22, 2025 at 07:59 AM, Daniel Conklin wrote:
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Yes, that's a good point too. The time I blew the diode on my power supply boards was as a result of having the wrong size barrel plug coming from my power supply.
