Yamaha ydp 131 no sound

[nosaj]

I have a yamaha ydp131 that was given to me for parts or fix. I get no sound from speakers or headphone amp. I have inserted signal from IC 402 at pins 1 and 7 and hear it in the speakers. One question is to test that IC should signal be input at the + or - side?

Service manual is to large to upload but here is a link to electrotanya https://elektrotanya.com/yamaha_ydp-.../download.html

Thanks,
nosaj

[The Dude]

I'd just check voltages on the op amp to see if it's shorted. I'd be more apt to believe your problem is in the digital realm. Have you tried a factory reset? Also check your lower voltage supplies, 5V, 3.3V, etc.

[nosaj]

I'd just check voltages on the op amp to see if it's shorted. I'd be more apt to believe your problem is in the digital realm. Have you tried a factory reset? Also check your lower voltage supplies, 5V, 3.3V, etc.

5v was good 3.3 was like 2.99 or so. Factory reset holding key on the far right while turning on, didn't change anything for me. I'll check the voltages on the op amp.

I'm up for any suggestions after checking the opamp. I have no history on it it was left for me if I wanted it. If I have to, parting it out is no problem.

nosaj

[The Dude]

There's also a 2.5V regulator. What's the voltage there? I worked on a similar model (although not this exact one) a month or so ago. The 3.3V was also slightly low. Scoping the regulator output showed some noise. I replaced the filter cap post regulator and brought the thing to life. I'm not saying your problem will be the same as mine, but the 2.99 volts might be a clue. You might have a look at C424 and/or C418. Look at the 2.5V supply also. If that is comparatively low, then I'd suspect C424 since it filters both supplies. If only the 3.3V is low, I'd suspect C418. Those supplies have to be pretty clean for things to work right. They will probably be SMD caps, but you can usually tack a regular leaded cap there without much problem if you're careful (if you don't have SMD caps readily available).

[nosaj]

There's also a 2.5V regulator. What's the voltage there? I worked on a similar model (although not this exact one) a month or so ago. The 3.3V was also slightly low. Scoping the regulator output showed some noise. I replaced the filter cap post regulator and brought the thing to life. I'm not saying your problem will be the same as mine, but the 2.99 volts might be a clue. You might have a look at C424 and/or C418. Look at the 2.5V supply also. If that is comparatively low, then I'd suspect C424 since it filters both supplies. If only the 3.3V is low, I'd suspect C418. Those supplies have to be pretty clean for things to work right. They will probably be SMD caps, but you can usually tack a regular leaded cap there without much problem if you're careful (if you don't have SMD caps readily available).

Ok ok ok ground reference is everything. previosly I'd left common lead for DVM on the analog board ground to check the digital regulators. Move common lead to Digital board ground. 3.3v and 2.5v good, scope shows flat line after the caps.

So ic402 all voltages VDC
p1-.01
p2-.09
p3-.08
p4-.01
p5 2.75
p6 2.75
p7 2.75
p8 5v

https://www.mouser.com/ds/2/294/NJM4580_E-218114.pdf

It doesn't look right on the voltages, so I'm gonna go back and measure and use c146 or c147 as common ground for meter and report back.
nosaj

[nosaj]

At this point I can get signal from the output of IC401 DAC so it's getting out of my level with Digital and SMD. The piano was free but I don't have the space for it. So I'm gonna tear it down save the analog section and the rubber key contacts, pots and other connectors.

nosaj