On this page I will go through the operation of the GHD Mk4 to Mk5 pcb to help people with fault finding and repair of the pcb.
What the pcb components do
|D2, R1||Trigger used to synchronize triac switching with mains sinewave.|
|R5, R6||Measure input voltage used to switch between 117v mode(100v - 150v)and 240v mode(200v-250v).|
|R10, C1, D9, C7 , C6||Power supply and smoothing|
|R7, R3||Pull up or pull down resistors|
Fault finding tips
|Fault symptoms||Possible solutions and things to check|
|Heating up to fast but not over heating.||Check R5, R6|
|Nothing happening when PCB is powered on.||
Safely testing PCBs
To test PCBs you should not directly connect them to the mains. You should use a isolating transformer to limit current and lower your chance of getting a shock. I just use a transformer from a shaver socket to power the PCB but do not try to run the PCB with the heaters connected.
I will continue to update this page when i think of more faults to add.