whistling noise coming out of the tv when watching tv programs through the set-top box. suspected leaky capacitors. opened set-top box and saw some "puffed" capacitors. the puffed capacitors are shown in the figure with an arrow.
De-soldered the capacitors and checked with multimeter, the capacitors looked ok, no leaks. If a capacitor is leaky, it will show some resistance reading in the meter. In this case, the resistance shown was infinity as a good capacitor should be.
Then I wondered what made the capacitor puffed? I had purchased a digital LCR meter recently. checked using LCR meter showed capacitor value as 100 mu F instead of 1000! , so as a result of deformity, the capacitance value had changed, thus de-stablizing the circuit.
I had a few 1000 mu F capacitors spare, so I checked their value, they also had gone down to 900 mu F, due to ageing perhaps, but, 900 muF would just work fine.
Replaced the three capacitors and connected back to TV. No whistling sound! So, what made three capacitors get deformed? Power supply surges might have taken the toll on the caps.
Investing in a good LCR meter paid off! otherwise, would have just replaced the capacitors. Measurements are good, measurements make you confident.
De-soldered the capacitors and checked with multimeter, the capacitors looked ok, no leaks. If a capacitor is leaky, it will show some resistance reading in the meter. In this case, the resistance shown was infinity as a good capacitor should be.
Then I wondered what made the capacitor puffed? I had purchased a digital LCR meter recently. checked using LCR meter showed capacitor value as 100 mu F instead of 1000! , so as a result of deformity, the capacitance value had changed, thus de-stablizing the circuit.
I had a few 1000 mu F capacitors spare, so I checked their value, they also had gone down to 900 mu F, due to ageing perhaps, but, 900 muF would just work fine.
Replaced the three capacitors and connected back to TV. No whistling sound! So, what made three capacitors get deformed? Power supply surges might have taken the toll on the caps.
Investing in a good LCR meter paid off! otherwise, would have just replaced the capacitors. Measurements are good, measurements make you confident.
