Repairing the power LED circult of a PS-018 220v-100v step-down transformer

yeah def a resistor... the rings on it are not clear??

 

It's as you can see in the photographs: The colour-coded rings are not even visible anymore.

Anyway, I'm probably going to get a 3W 4.7K ohm resistor, since I don't know the exact specifications of the LED itself at all. Giving a more generous resistor will be safer, especially since the formula gives the following: R=V/I=(115-1.8)/0.025=4528 ohms and P=I*I*R=0.025*0.025*4700=2.9W.

I've also realized that a 3W resistor is already going to be bigger than the original one, as it looks like a 1/2W resistor.

 

Using a resitor of 4.7 Kohm (too much teorically calculation XD) at first spike of voltage can you burn easly the LED. Much better a LED powered with 20mA (and 120V) wich have less light, but produce less heat and not burn easly than a one wich is powered with 25mA but has the only advange of better light. The W of a resistor don't afflict the led brigth or his "perfomance", but a resistor with an high Wattage can dissipate much heat (BTW it's true after a certain W value you need a heat dissipator, but this is not the case).

 

Well, you brought up a point that I didn't consider lol. Here, we don't have voltage spikes at all... or at least, I haven't encountered one in a very long time. :/

I don't actually know the forward diode current of the LED, so I assumed that it would be 25mA (Since it seems like normal red LEDs have a forward current of about 20-30 mA).

Alright, so I'll go for a 5.6K ohm resistor, to allow up to 140V. The PSU board of the SCPH-10000 will probably activate it's fail-safe mechanism around that voltage anyway.

 

Thank you all. I've gotten both my step-down transformers repaired.

My PS-018 step-down unit now has a working LED, and I didn't even need a diode. I figured out that unlike what many people said online, the truth is that the reverse voltage and current will not be too high for the LED because of the resistor.

I used a single 5600 ohm 5W resistor, and have added an additional 100V outlet socket at the back of the unit for by HDD unit.