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Old 17th March 2011, 06:19 PM   #1
rrae is offline rrae  Norway
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Join Date: Mar 2011
Default How to test TDA8947J

Hello,
I have PC speakers that isn't wokring well - sattelite speaker channels wasn't working, only sub channel work properly. I was looking at PCB, saw that there is blown capacitor, replaced it, tested, now only sub and right channel working, in left channel I can hear music, but when turning volume higher, it doesn't change. I think that TDA8947J is gone bad. How to test it? Don't have scope.
Thanks.
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Old 17th March 2011, 07:41 PM   #2
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First step is to disconnect the speakers and measure the output voltage with no signal present. Pins 1, 4, 14 and 17 should measure about half the supply voltage. If either of them measures full supply voltage or 0 V, the corresponding channel maybe blown.
You can check that by removing the IC from the PCB. Then measure continuity with a DMM. There should be continuity from pin 3 or 16 to either output when the negative probe is at the output and no continuity when the positive probe is at the output. There should be continuity from either output to pin 2 or 15 when the positive probe is at the output and no continuity when the negative probe is at the output. If you have continuity in both directions, the corresponding output is fried and you need a new TDA8947J. If the continuity checks OK, you will have to look for other faults on the PCB, like shorts, interrupted traces or defective components. In view of the small amount of components you may replace them all just in case.
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Old 17th March 2011, 09:08 PM   #3
rrae is offline rrae  Norway
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Thanks for the great reply. Measured TDA, all was fine, so I was looking at IC, found leg that is unsoldered. Now all working fine.
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