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About Rick Montgomery
Expertise
Most questions about 1970's-1980's audio equipment. Most 1980's -1990's VCR's and VCR combo's. Most 1980's-1990's car audio, except original equipment. I know name brand after-market such as Kenwood, Pioneer, JVC, and some Sony. I am not so good with TV's, DVD's or camcorders. I do not work on Projection TV sets at all. I also have no access to documebntation for sets outside of the United States.

Experience
Professional Electronics Technician since 1975, specializing in most audio, home, portable and car. Also all VCR's. Limited TV knowledge. No projection TV experience

Organizations
Through work, NESDA.

Publications
n/a

Education/Credentials
High School. Graduated with 2 yrs Vocational Electronics in High School.

Awards and Honors
Certificates of completion of factory training seminars for various brands

Past/Present Clients
Thousands of customers to the Service Centers I have worked for.

You are here: Experts > Home/Garden > Home Appliances > TV/VCR/Stereo Troubleshooting > sony audio/video control center

video control center

Expert: Rick Montgomery - 11/5/2009

Question
rick, i have a sony audio/video center str-d915. was using it as normal and suddenly all sound stopped and the digital display disappeared! turned it off and on.. not change. turning it on lights up light on volume knob and the dpc mode light, but no display, no sound no matter which in put mode. is this thing toast or what?

Answer
Wind,
You have a somewhat older Sony Receiver. I would suspect that your main 8 amp fuses are blown. This happens usually because at least one set of the output transistors are shorted. When they go, they usually take some of the peripheral circuit with them before the fuses have time to react. The output transistors are mounted on the large heat sink, and will have the numbers MP1620 and MN2488. You will also want to pay close attention the the protection transistors, 2SA788. Check them in all 5 channels, not just the one(s) that are shorted. If you miss any, you will short out another set of outputs. You will also need to check the emitter resistors. These are the 3-legged white cement resistors. They need to be 5 watt. If they are not, serious damage can occur by allowing current to flow after something has shorted, and it will take out more components before/if the fuse blows, increasing your repair cost.
But before you personally attempt to repair the set, or take it to a Service Center, be sure to closely inspect the speakers and speaker wires, as 9 times out of 10, they are the cause.
Actually, I have seen few cases where the speakers were the cause, unless they were overdriven, such as by a teenager for very loud music, or to entertain a block party.
Speaker wires though, are a common cause for this type of failure. Everything from too much insulation stripped off of the ends (you only need 3/8" stripped off. Just enough to make the connection), to splices, a DEFINITE no-no for any speaker wire. Or running the speaker wire under furniture, and having the weight of the furniture crush the insulation and allow the wires to touch. Remember, it only takes ONE STRAND from the positive side touching ONE STRAND from the negative side to cause this type of failure. If you have inspected the wires, and have assured they are in good shape, and are ALL at least 18 gauge SPEAKER WIRE, then find a way to test the speakers. If they are all good, then proceed with repairs.
regards,
Rick

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