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Unbelievable! Shorted E-Cap In Sony DVD Hi-Fi
This Sony DVD Hi-Fi came in with the complaint of no power and surely the standby LED would not light up. The first thing I did was to open up the cover and head straight to the power section. This model still use the linear transformer and the main fuse did not blow.
If it blows into dark color, this means there is a serious short circuit.
I checked the incoming 230 volt up till the transformer primary but there was no secondary output voltage. There could be two reasons when there is supply voltage input but totally zero volt output. The first cause would be the primary winding open circuit. For your information, secondary winding rarely open circuit. Next cause was there is a shorted component along the output DC line to ground or the mainboard is shorted.
When I placed my ohmmeter to DC line and ground I saw that it has very low ohm reading either way indicating there was a short circuit. I checked on the secondary filter capacitor first (1000uf 25 volt). By removing the filter cap I noticed there was no longer short circuit thus this confirmed the e-cap is the cause of the short circuit.
I tested the suspect e-cap and it was proven to have short circuit-see the photo below:
Usually when an e-cap is bad, it is either ESR ohm very high or the capacitance value out but this e-cap is shorted (considered zero Ohm already).
Just to test out if the shorted e-cap is the only cause of the problem, I put in a 470uf 25 volt for testing the output again.
As expected, the power came back (see the two photos below).
Conclusion- Assuming if the secondary output e-cap is good then I need to check and troubleshoot on the mainboard to locate the short circuit. For those of you who wants to be good in checking electronic components, I can recommend Jestine Yong’s ebook HERE.
This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.
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