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QMX Draws 200mA when Power Applied

 

Hi All,

My QMX had the short between Q103/Q104 which was discovered before powering it up.

The AOD403 was replaced as the original one fractured with modest pressure applied with the heatgun.

The QMX was powered up tonight with 7V on a current limited supply to 250mA output.??
Current draw is about 200mA when power applied without switching the unit on.? The display is blank.??
Has this happened to anyone else???

Cheers,
Glenn VK3YY.
 

Plug in PCB #1 connector voltages after applying power:
Gnd = 0V
+12V = 7.15V
VCC = 1.2V
ADC_5V = 0.6V
PWR_HOLD = 7.17V
V_IN = 7.17V
PWM_5V = 0V
PWR_ON = 7.1V

Plug in PCB #2 connector voltages:
ADC_3V3 = 1.1V
VDD = 3V
GND = 0V
PWM_3V3 - 0V
LIN_REG_EN = 6.93V
+12V = 7.06V
 

Hi Glenn,

There is a short somewhere. ?VCC (5V is getting pulled down). ?Also what concerns me most is the LIN_REG_EN signal. ?It is supposed to be at logic levels (0V to 3.3V) and is directly connected to the cpu. ?unfortunately, that kind of voltage on the cpu is usually not healthy for that chip.
 

Thanks Jeffrey,

I found a solder whisker bridge from the plug in PCB#1 edge connector to the FET.? It turns on with the switch now, I hope there isn't any damage to the CPU.
 

It seems to be ok so far, firmware loaded and the display is working.??

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