Power transistor somuch heat

 

They get hot when they are working hard - it's physics.

If you need to keep it within operating limits you could try the appropriate sized heatsink.

https://www.heatsinkcalculator.com/heat-sink-size-calculator.html

 

Welcome to AAC.

What transistor, where? You mean Q109? Post the schematic, it almost certainly will need a heatsink.

 

probably Q110 too, arent they in some kind of push-pull configuration?

 

Hello,

Both Q109 and Q110 have boxes drawn on the pcb.
That is likely the space reserved for a heatsink.
When a transistor has to dissipate quite some power, a heatsink is used to help the transistor to withstand the dissipated power.

Bertus

 

yeah but it is completely strange that the Q110 heatsink space is in collision with the capacitor, which is drawn as horizontal by the manufacturer, unless this is some prototype PCB. I mean I dont argue that heatsink is nessessary I am just amuzed by the collision.

 

Power transistor so much heat

No real question . So will guess.
Yes, a transistor is in simple terms , a variable resistor .
Ok technically a variable conductance , but let's keep it simple .
The resistance is varied by the base voltage changing ( ok very simplified and a guess on your circuit ,) and the changing resistance caused the output voltage to be changed .
Power is dissipated as heat.
Power = V*V / R
Where V is voltage across , R is the resistance .
As the resistance of the transistor is changed , the power changes

When transistor "off" R is "infinite" , power dissipated is "zero"

When transistor is hard "on" , resistance is "zero" and power is limited by external circuit ..

Any point beyween on and off , power is dissipated in the transistor .

So what's your question ?

 

Without a schematic its impossible to say what's needed.

OK, there probably isn't one available. SF2389 is a commercially available PCB, It is the AC/DC converter/charger for a battery powered 16" fan. As shipped it has no heat-sinks installed so probably doesn't need them unless this is faulty. My guess is they are related to the speed selection.

 

what interference?

 

Heat sinks work best when actually connected to the device that needs cooling.