![]() Then do the math backwards in order to calculate the "top voltage" of the resistors. Find the two resistors that are connected to the "REF" input of the TL431 and assume that there is always 2.5V on that pin(because there is, due to the feedback). Trace out the circuit and see what is going on. This is the amount of resistors needed to implement a simple type 2 controller. ![]() In your case the TL431 is clearly marked on the board and there are four resistors and a capacitor next to it. So the trick is: You can just read from the resistors what the output voltage rating is supposed to be. You feed the output voltage of the SMPS to the TL431 though a voltage divider that divides the output voltage down to 2.5V when the output is at its nominal voltage. It is hooked up in such a way that the transistor pulls the current needed to keep the "REF" input pin at the value of the voltage reference(2.5V. It can be a little tricky to understand, but it is basically a voltage reference, an opamp and a transistor. In all regulated power supplies, the output voltage is monitored and fed back to the regulator(via an opto for isolated supplies). Here is how to actually determine the output voltage of the SMPS. So 18V seems like a reasonable guess if i get no answer on here. I am inclined to think they found that adding an internal identical psu would make their product cheaper and didn't change any internal electronics. I've seen that there exists an older Bigben TW1 model whoch has an external PSU, an 18v one. The model in question is a "Bigben TW6" with in this case paris themed stickers on the side. Or more likely if someone can determine the output voltage of that psu based on it's picture. I'm asking here in the unlikely event someone here owns the same tower or a similar one from thomson/bigben Is there a way to determine the voltage output of that internal psu? There is no writing on the thing. The PSU is broken and rather than starting to solder/desolder components on the thing I'm looking to just replace it. Someone asked me to look at their broken docking station/music player.
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