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How To Repair Amplifier No Sound
A customer of mine brought to me the TAC Integrated Stereo Power Amplifier With the Model of AV-355 for repair. The complaint was no sound but have power. Usually the first thing I do was to connect a speaker at the output jack to see if the sound really not present.
Another test is to check the output DC voltage at the speaker output jack. It should not have DC voltage and from the test I got 35.6 DC volt which mean the internal power transistor had already shorted.
Alright, once the casing was removed I could see two circuit boards (main and pre amp) and a big toroidal transformer-see the photo below:
From the visual inspection, I found two e-caps bloated on top of the capacitor casing, broken jumper wires and a burnt resistor-look at the white arrows in the photo below:
I knew if a burnt resistor were found this means the main power amplifier transistor will be shorted. True enough, when I placed my digital multimeter to the transistor pin (on board) I got very low ohm on all the legs (pins). From experience, once you have found a shorted power transistor, you have to check all related components around that circuitry. If you want to learn how to accurately test electronic components you can check out Jestine’s Ebook HERE.
After spending some times to check the circuit board, I can’t believe that there were actually 15 bad components found which include the burnt resistor.
After the replacement with new components the stereo power amplifier with no sound problem was finally fixed. I did not post the video thus you would not hear the sound but the sound worked!
This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.
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Note: You may check out previous post about fixing active speaker in the below link: