The voltage measured at the output of the USB (power module) was equal to 14V70 and sometimes dropped to 14V30, especially in strong heat. when it fell to 14V30, the base module software detected an undervoltage: red flash, and off the displays. Then the voltage went up to 14V70 and the displays turned on again showing 00 <00 and the power-on detection cycle started again.
To remove the fault, there are several possibilities:
- increase the resistance marked C12 (!): not tested
- Change the value of the detection threshold in the firmware: not tested
- Power the clock with a more stable power supply:
Solution that I chose.I used an old 19.6V 3A HP notebook PC and I completed it with two LM317 adjustable (parallel) controllers to get 15V8 3A. I chose the value 15V8 so as to compensate the 0.8V drop on the diode D1 of the power module. As a result, the base module is supplied with 15V in a very stable manner.
The problem is gone , the clock stabilizes immediately when it is levitated, and the undervoltage alarm is gone.in attached document is the LM317 schema I used to complete my 15V8 power supply