When electrolytic capacitors are unused for a long time, the dielectric made of aluminium oxide may deteriorate, allowing DC current to flow -> the capacitors become leaky. A basic capacitor tester is unable to measure this leak, but it may show confusing results. In this case, I am testing an electrolytic capacitor inside a radio Continue reading

Leaky capacitors are a common cause of problems with electronic equipment. By leaky, I don’t mean that the capacitors puke out their own viscera, but that they are conducting a certain amount of DC current. This leakage cannot be tested with a just a multimeter. Capacitors used in vacuum tube circuits are often subject to Continue reading

The PSU was tested using a 2.2kΩ resistor as dummy load, which when set to an output voltage of 180V, caused a current draw of 80mA. Oscilloscope measurements show ripple voltage of 3.5mV RMS (the probe is in x10 mode). This gives a ripple factor of 3.5mV/180V = 0.002%. Not bad for a DIY multifunction Continue reading

The project started with an LED TV with presumably defective backlight strips. It’s time to find out: Internally, the LED strips are connected in two different series loops, and markings on the TV PSU indicate that these loops shall be driven by 100V and 111V respectively. I connected the test instrument to one loop, set Continue reading