Yamaha model P121 damaged, no audio

Synth Repair
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1

Yamaha Model P121B, No Audio

I made a stupid mistake, and plugged in a 58V Ebike charger by mistake. Ouch!

Tests done:

  1. The LEDs still light up, and change correctly when I press different modes.

  2. The input jack board is still switching 12V on/off.

  3. On the main board, there is an IC with a crater blown out of it (IC29).

Photo of IC29 with hole in it (on left, center of (I think) 4 inductors, labeled 100.

IC29
IC291920Ă—1440 300 KB

Questions:

Should I replace the main board and pray at about $250? I am curious what might be fried in the keyboard action section. I have not delved into that yet.

Is it worth it to try replacing the exploded chip, if I can identify and purchase it? (The “crater” took out some of the identifiers.) My guess is that there must be more damage than just this chip because 58V was applied.

Thank you very much to all that took the time to look this over.

Dan

2

mReplace DM. Did you inspect the JK board? The voltage spike could’ve fried it too. This feeds V to DM

3

Thank you, yes, the JK board is switching 12V on/off properly to the main board.

4

The chip is likely to only cost a few dollars so might be worth a try first.

5

That’s the D-Class Power Amplifier chip - YDA176-QZE2 - good luck finding that - seen it some time ago on ALIExpress for something like $26. But that is surface mount and needs some special tooling to remove.

1 Like
6

wernersaurus Thanks for the info.

I ordered it (believe it or not) on EBay. It should arrive today. I have the tooling to R&R this chip, but after the 58V blasting I gave his board, my hopes are not high.

Thanks again, this confirms the part number.

1 Like
7

Wernersaurus and sargfowler are correct.

Special desoldering equipment was called for, and the chip was cheap enough to give it a try anyway. After making an embarrassing mess of the board removing the old IC, I ordered the complete main board from Syntaur (they had the best price as well). I will try out the new board in about a week, and I have high hopes.

I made a home made hot air desoldering arrangement that removed the IC, but the board was damaged in the process.

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The new board fixed it! I will mark this thread solved. Thanks to all.