Sony str-de675 receiver has no sound at speakers when turned on.

This unit is having a problem with the preamplifier and power amplifier section. The reason to suspect this is that you can still hear sound, this is not likely if you ahd a failure in the power supply section. The unit may have had a failure in the amplifier areas of these sections, These are the signal amplifier sections that increase the power of the signal to drive the sound in the speakers .The Unit is probably in the protection mode reducing all power to prevent further damage to the rest of the receiver. You can go to the www.sony.com website support section and look in the frequently asked question and troubleshooting sections for problems like yours and see if they have any answers. On this website you can also find customer support. Ask them questions about the problem and see if they have any solutions.If all this fails to answer you problem, you can try opening the unit and looking for the problem yourself. Only work on the unit with it unpluged from the power source. Take off the top cover and look for any damaged areas, on the pc boards.They would be brown areas from excessive heat due to component overheating and possible failure.Look for capacitors that may have gone bad, they will be bulging from the top and bottom and may be leaking material from inside of them. Any component like this needs to be replaced. You may find burnt resistors and other failed components that will require a digital voltmeter to test.If you have expperience with this type of repair you might be able to isolate the problem and replace the parts. This may require the help of service information due to the complexity of the receiver's operations. Try to get a schematic or service manual from the web or a repair shop. This will have all the parts and a diagram of the all the different sections of the receiver. Usuall there is a power supply section, a tuner section, a preamplifier section, and a amplifier section. There also could be a equalizer section and other sections according the functions of the receiver. The failure most likely has occured in the preamplifier section or amplifier section. The problem in the preamplifier section could be a signal diode failure or a signal amplifier failure. in the amplifier section the problem could be in the output power devices which may be transistors or ic's depending on the type of output amplifier use in the unit. Usually not that hard to find with good service information and test eauipment.You may want to take this to a school that teaches electronic servicing and see if they will work on the unit for you for the cost of parts and a small labor fee. Call them first and see if they can help you out. I hope this helps you with your problem.