J12345

I've been going off of this datasheet, which agrees with what you've said. I'm probing the bottom left and top right pins, 4 and 8 respectively. I have also discovered that when I probe pin 8 (VCC) against ground I get my 2.72 volts. However, if I probe 4 (VEE) against ground, I get .02 volts. I don't know enough about op amps to determine if that acceptable. My understanding (from YouTube) says they should have equal and opposite charges, so it needs a negative charge? Excuse my electrical ignorance, but is that even possible with a standard wall outlet? The text on the module I was talking about having 5v reads 'Casio CA6722 801 423'. I've updated the image in the original post to be clear. The only reason I traced the voltage back to this module was because I thought 2.72v was a little on the low side when I first probed it. I found that it went CA6722 > 5v > resistor > 2.72v > pin 8 of op amp. This information may be relevant. Edit: words are hard.

I was getting 2.72v across my op amp. I suppose I could just desolder and test each component individually. But I was thinking, since I can't find a clear tone out of any part of the board with my audio probe, would that mean it is whatever generates the sound in the first place? I'm not sure what component does that. Though, since the tones I'm getting out of the Key to Board ribbon don't seem to be a 'final product', maybe it's feeding the 'processor' of tone bad signals to begin with? (to be clear, nothing I get out of the Key to Board ribbon shown above in the Full Keyboard image sounds like the scratchy tones I'm getting elsewhere on the board, it just sounds like madness) edit: for everyones info, this is a 9v board. I tested one side to ground and got 2.72v, followed that back to a resistor that had an incoming 5v, then back to the module on the right side of the M4254 Board image, above the big capacitor, with the heat sink. I'm not sure what that module does, but the pin with the highest voltage on that module was around 8v.

I didn't pay the volume control much mind, but I'll check it out a little further. Since I wasn't getting any clear frequencies going into it I didn't expect it to be the issue. Same goes with the op amp. I looked up the data sheet here and my input and output signals are pretty much identical and I am getting 2.72 volts across my voltage inputs.

The volume control doesn't seem to change the volume. I am getting 9.07v at the power input, which was swapped out by the owner of the keyboard.

Hello, I am trying to repair a Casio CT-460 for a friend. I am equipped with an multimeter and a home made audio probe. The keyboard is making very little noise that is also buried under static. I can hear the tones play faintly when I press a key. This also applies to the 'Demo" track that plays when the demo key is pressed. I also cannot find any point on any of the boards that doesn't have a layer of static. I've probed pretty much everywhere (including places I shouldn't have) though there are placed where the tone is much louder. Specifically on the D23C module on the M5257 Board shown below. I had the idea to probe all the conductors in the Key to Board ribbon shown below, but the tones I got out of there were strange and nothing like what the speaker outputs. I've removed a speaker because I kept having to flip it with the board and that got annoying. I'll put it back on when/if the keyboard is repaired, but I didn't want the loose wires to confuse anyone. If anyone has any guesses as to what should be checked/replaced, any suggestions would be appreciated! Underside of the Full Keyboard: M4254 Board: M5257 Board: