Heater PCB Resistor gets really hot

Vertex 3D Printer Vertex - Wiring and electronics
1

Hi everyone,

I had a problem with the fans, one of them was shorted at the screw terminals. As soon as the printer wanted to turn them on, a resistor on the heater PCB released the ‘magic smoke’. I found the schematic of the PCB here, and noticed the resistor R1 is in series with the fan. I presume this is a RC filter for the PWM signal, to drive the fans. I replaced the burned one with a new 10R resistor but as soon as i turn on the fans at 50% for example, the resistor gets really hot… i measured temperatures over 80°C (180°F)… I’ve done the calculations and it dissipates half a watt, while those are rated for a quarter watt at maximum…

Any idea what could gone wrong? The fans drawing too much current?

Thanks in advance for any reply!
Christophe

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2

Hi Tixhyl,

This resistor (lowers the voltage from 15V to 12V) power rating is indeed a bit on the low side and it turns really hot when the fans are blowing at full speed. Doesn’t burn though.
A 1/2W resistor would have been better.