Damaged resistors

Hi All,

I am being told be a supplier that standard UK mains spike could damage the resistors in this circuit. Can you take a look at this circuit diagram and answer the following questions

A:Would would be the voltage required to damaged R36 & R47
B:In your opinion would this be possible with standard UK mains


Thanks

Steve

1u gives 70mA in full wave. You have 2 in series = 35mA 35mA through 180R = 250mW
Voltage to damage would be 1kv

Hi Colin,

Thanks for the reply, what does the 1u mean? <- Ignore this I was being stupid

Steve

Scarr said:

Hi Colin,

Thanks for the reply, what does the 1u mean? <- Ignore this I was being stupid

Steve

Click to expand...

C39 and C42. They are labelled as 1u on your schematic rather than 1uF.

In addition to a fairly long duration high current damaging a resistor, a short duration voltage spike can also damage a resistor by its arc. The resistor might be rated at only 300V when the normal peak voltage of 240VAC is 340V and a spike will be much higher.