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I have the following device, which basically contains 18 songs. we can play the next song by switching the switch on and off. It also has a volume control. enter image description here

Recently it started to buzz a lot and the song was suppressed, the volume control was dead (it had a constant low volume)and the switching operation didn't work. So I opened it,

Pic was taken before replacing the Capacitor

After doing some research, I replaced the 1000 MFD capacitor, The buzzing dropped a bit, but all the other problems persisted. My Questions are,

  1. Please map out the basic working of this device (like the amplifier followed by speaker etc).
  2. The buzzing is because of the unfiltered noise or the transformer. I took the transformer out, but it dint seem to make any noise, the noise was from the speaker.
  3. What's the solution? (why did the volume control and switching operations went out?)

These are all the components,

enter image description hereenter image description hereenter image description here

Surprisingly, when i replaced the capacitor, i heard a random song (which probably wasn't there in the 18 songs), Finally, is there a receiver circuit of some kind?

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  • \$\begingroup\$ How is the device powered? Does the buzzing correspond to the pitch of the mains frequency in your area? \$\endgroup\$ – Platytude Jan 9 at 3:54
  • \$\begingroup\$ Extract the schematic. \$\endgroup\$ – analogsystemsrf Jan 9 at 4:07
  • \$\begingroup\$ Looks like a diode bridge at the top of the second photo. Check each, one may be shorted. A good diode should have ~0.6 V forward drop and "infinite" reverse resistance. \$\endgroup\$ – DrMoishe Pippik Jan 9 at 4:14
  • \$\begingroup\$ @Platytude It's powered from AC mains (50 Hz, India). I think the buzz is near 120 Hz (I'm not sure, i just checked the audio in this link, psaudio.com/ps_how/how-to-find-and-fix-hum) \$\endgroup\$ – Aravindh Vasu Jan 9 at 4:26
  • \$\begingroup\$ If you want someone to help figure out your circuit, you'll have to follow all of the connections and produce a schematic showing every component and the connections between them. It will be difficult for you to find out what the chip under the bump of beige potting compound is. Higher resolution pictures from better angles would help with trying to spot surface defects. Just speculation, but if your buzz is around 100Hz and replacing that cap decreased it, perhaps it could be mains noise from after the rectifier. \$\endgroup\$ – K H Jan 9 at 5:15

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