====== In order to boost the ouput voltage from 12 volt to 13.8 volt ======

  * You cut all wires coming out of the supply keeping only the various 12 volts wires which are soldered together and also 1 wire giving 5 volts  .
  * locate the Pulse Width Modulator which drives the switching  transistors .It is the brain of the supply !  Generally  it is a small digital circuit  (reference TL 494 or something  else ending with 494   having 16 pins ) .
  * To increase the output voltage  you only have to put a resistor between pin 1 and 7  .
  * The value has to be adjusted in order to get the 13.8 volts at the output .(the value is between 10 and 20 Kohms )((la prochaine foi tester directement à 10k))
  * It should be noted  that for some power supply ,to have  a good regulation of the output , it is necesary to load the 5 volt circuit  with a resistor in order to have some current anywhere between 0.5 and 1 amp .