Dropped Karaoke Machine

[Owl Eyes]

Greetings. I have in my possession a broken Karaoke machine that I have been asked to fix for a friend. It was being used in a middle school chorus class when unruly 6th graders knocked it to the ground in a Karaoke driven frenzy. The Video still is functional, and the menus still navigate, however the audio is non-functional. I disassembled it upon returning home with it hoping to find a simple desoldered connection, but was not so lucky. My probing revealed no obvious breaks but obviously something is not right. So far, I have no ideas where the damage might be. Any thoughts would be greatly appreciated.

Ps. It is a Memorex Dvd + Cassette Mks2422 made in 2005.

 

[duffy]

Breaks are not always obvious - they can be inside the plastic insulation of a wire with the insulation still held by a crimped contact, in a cracked ring-shape around a connector pin on a pc board, one broken lead under a big electrolytic cap still held to the board by the remaining pin.

Look again at the heavy stuff. Those big caps I mentioned, wiggle them with your finger. A board-mounted transformer, look at the connections with a magnifying glass under a strong light. The parts with heatsinks, study the pins on the underside of the board - see if anything moves when you flex it.

Check the pc board itself for cracks. Look especially around the areas close to the mounting points.

Can you hear anything from the speaker? The least bit of hiss or hum will tell you that part is still connected and you need to look upstream somewhere. If there's no sound it might be in the connection there - or it might be in the power connection to the amplifier, especially if it is on a separate board.

Do you have a meter? The speakers should read 4 - 8Ω. This isn't exact, but you are looking for a break. Turn it on, check DC voltages on the pins under the big filter caps. You should see something - maybe +12V, maybe +20V, but if it's zero then there's a break to the power for that section.