Fan speed control circuit 4 bc639 transistors are used on the circuit speed can be adjusted with potentiometer 47k. Intel CPU fan circuit used in the circuit tests based on phenolic hole about a new simple circuit for the low cost ..
Source: http://www.soloelectronica.net/fan_espeed_control.html
500W Power Amplifier Circuit Apex B500
Apex B500 power amp’s pcb design stylish been output mje15032 and mje1503 power transistors used supply voltage symmetrical 55v … 90V from quite high dangerous circuit tests, be careful addition amphitheater to be used with fan control and protection circuit diagrams and PCB drawing is on.