Marconi 2024 9kHz-2.4GHz signal generator, arrived this morning, fixed in 30mins by replaced a capacitor in the power supply. I have to do some cleaning later ![Grin ;D](https://www.eevblog.com/forum/Smileys/default/grin.gif)
After about 6 years, this unit failed again! There is no response after pressing the power button, it seems that the SMPS is broken again.
I opened the case and measured and all the rails had no output, so I took the power module out to check and didn't see or smell anything wrong. However, just when I tried to flip it over in order to inspect the bottom side of the PCB, I was shocked badly.
![Scared :scared:](https://www.eevblog.com/forum/Smileys/default/scared.gif)
My ring finger hurts so much! Yes I know that the capacitor must be discharged before repairing the switching mode power supply, but I clearly saw that there are two discharge resistors on the PCB, and this electric shock should not happen! I checked the 4 capacitors (2S2P) next to the rectifier bridge with a multimeter, two of them measured 250V and the other two measured 0V, so I found a suitable resistor to discharge those two dangerous capacitors.
Then I removed the two discharge resistors from the PCB for measurement. One of the resistance values was a normal 100K, and the other was measured as an open circuit.
I found two 150K resistors, they are a bit big in size, but still fit into place on the PCB, after soldering them I put the power module back in the case, connect all the cables, press the power switch down, and it works!