EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: atferrari on November 25, 2014, 08:39:07 pm
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Genius speakers set for PC. Model SP-E120
Audio amp inside is SJ2025. I could find the datasheet in Chinese language only.
After replacing the dual pot damaged when falling from a desk, I noticed that at low level (pot progressively CCW) the audio output is more and more blurred, the lower the noisiest. That is awful!
With the pot fully CW, (maximum output), no matter what input, audio in the speakers is good.
The IC is hot to touch but I see that in the bottom, 4 pins (2 on each side) are soldered to what I believe is a thermal pad, with a generous amount of solder.
My daughter insists that in the past it worked OK at low levels.
At least I would like to know what to look at before giving up here. Two pots already changed and the main filter cap as well. Caps look OK, no leaking nor bulging.
Self esteem is at stake here.
Gracias for any help.
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I think that the SJ2025 is a china version of TEA 2025, from the datasheet it looks like this circuit is some what unstable and need a lot of decoupling caps. You should check with a scope for high frequency oscillations in case some of the caps have been knocked loose or destroyed in the "accident". Is there two bridged amps or only one for left and right speaker? Have you checked the DC voltage on output 1 and 2. How hot is the amp (max power with no sound 0.5W and it should be less than 40C). Not much help, but not to much info fore me to work with.
TEA2025 Datasheet http://www.st.com/web/en/resource/technical/document/datasheet/CD00000172.pdf (http://www.st.com/web/en/resource/technical/document/datasheet/CD00000172.pdf)