If anyone has the patience , Im in need of guidance

Hi Guys First off I have no background of electronics so please bear that in mind with your answers . I have a sony amplifier TA-FB730R . This amp has just ceased to work . No lights sounds nothing . I have changed the fuse on the plug and had a quick look for any obvious fuses inside , of which I can not see any . I have basic knowledge of how to solder and the use of a multimeter . Basically is there any easy checks I can do to see if this can be revived , any websites that might give guidance or any other info anyone can share with me . Merry Xmas & A Happy New Year Thanks In Advance Regards Dave

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david_ian_hall
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First, use your multimeter to check that you have line voltage on the power transformer's primary. You might have to do a little wiring tracing to identify the primary terminals, but it shouldn't be too hard. If no line voltage on the primary, look more closely for other fuses. Also, check the power cord and power switch on the amp for continuity. If you have line voltage on the primary, do you have any secondary voltages? Check the other terminals for voltages. If no secondary voltages, you probably have a blown power transformer. Check the primary winding(s) for continuity. You should see ~100 ohms or more on the primary. These transformers can have a thermal fuse INSIDE the transformer. You'll have to tear into the transformer for that... It will usually be on the outside of the windings, but under the outer insulations. If no thermal fuse inside, you have a bad transformer that will have to be replaced with either an OEM replacement part (you'll probably have to order through a Sony service shop) or a generic replacement (you'll need to know the original transformer voltage and current ratings to identify a suitable replacement... good luck on that one). If secondary voltages appear to be there, the most likely problem is failure of the output devices (BJT or FET transistors). You'll need to unsolder these from the circuit in order to properly check them. The usual failure is one or more shorted transistors. Resistance checks on these will show very close to zero ohms on your multimeter (be sure to use the diode setting on your multimeter). If you do have shorted output devices, be sure to check the transistors in the circuitry immediately preceding the outputs. One or more of those will probably be bad as well.

If none of these checks get you in the ballpark, you'll need to find a good service shop. Good luck on the repair.

--
Dave M
MasonDG44 at comcast dot net  (Just substitute the appropriate characters in the 
address)

"In theory, there isn't any difference between theory and practice.  In 
practice, there is."  - Yogi Berra
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DaveM

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