Sony dav-sb300 has a crackling sound after a time

Ginko

• 19396 Answers
• Posted on Aug 18, 2011

SOURCE: MY SONY DAV-SB300 DOES NOT

Hi.

Check carefully power cord connection. That is often the reason for no power problem.

If the power cord is OK the problem is a defective power board. Sometimes it is possible to see visually that the power board is defective because the capacitors on board look bulged. Before testing the power board it is necessary to disconnect power and to discharge PSU capacitors shorting the capacitors contacts with a screwdriver. Example of discharge points are shown below:






After that, if there is nothing unusual at a glance, testing will follow reading impedance on single components and circuit. Testing starts from power cord impedance (it must read zero from plug's prongs to solder joints on PSU), resistors and diode in AC section of PSU, near to the power cord attachment. Next part of testing is done with power on, tracking voltage from AC section of PSU down to connectors in DC-DC section of PSU. For safety reasons testing must be done by a trained person.