No sound from Yamaha digital piano

[Pianomancer]

Hi All,
I have a used Clavinova CVP 209 that isn't playing any sound from the keys or memory, neither on headphones nor line out. The speakers work OK from line in, and the rest of the lights and screen seem to work just fine.

I have tried doing a factory reset by holding down the top key and turning it on, but that doesn't help. I did the RAM/ROM checks and they're OK. I checked the volume potentiometer and it seems OK (works with line in audio). I'm thinking it might be faulty DACs from the synth board (IC 28 and 29: ) or op amps. Not sure how to narrow it down more. I've scanned the boards for bad capacitors, but only found one that's slightly suspicious but on the mic input circuit which shouldn't affect anything anyway. Does anyone have experience with this? I don't have an oscilloscope so I can't do any precise voltage checks beyond multimeter checks.

[stj]

Re: No sound from Yamaha digital piano

you can use a small amplifier for tracing audio signals - just join the earths together and use the amp input as a probe
you can start by checking the dac output to see if it's an analog or digital problem

[Pianomancer]

Re: No sound from Yamaha digital piano

Do you mean use an audio cable to probe around, and connect the ground section of the cable to the instrument's ground? Should I use a resistor in series for this? It's hard to tell what level of damage I'm dealing with poking around like this

[stj]

Re: No sound from Yamaha digital piano

well if the amplifier is battery powered and you use a film capacitor like a .1uf in series then you can really damage anything unless you probe high voltage like mains

i used to use an old powered pc speaker.

[Pianomancer]

Re: No sound from Yamaha digital piano

I tried probing the DAC output pin using the aux in cable. There was no sound. I was using a resistor though instead of a capacitor... oops. Would that make a difference? Can I conclude from not hearing any signal from the output pin that the DAC is bad? That would mean both are bad, one for each channel.

[stj]

Re: No sound from Yamaha digital piano

resistor will reduce the signal, a capacitor will block dc
if both dac's seem dead then more likely a voltage is missing or an enable line is missing/stuck

[Pianomancer]

Re: No sound from Yamaha digital piano

If you could educate me, why would a capacitor block DC, and why would I want to?

The DACs are getting voltage and I assume they are getting clock signal from the CPU just fine. I probed the opamps and injected analog signal into their outputs and I got sound, so that leaves the DACs being the problem. I'm not sure how they would both go bad, but it is 20 years old and it was pre-owned so I don't know how long it was operating on mono. I think I'm going to order a couple of these ancient DACs and try to solder them on.

[stj]

Re: No sound from Yamaha digital piano

shouldnt you be injecting sound at the dac output pin to confirm the analog stage is good?

[Pianomancer]

Re: No sound from Yamaha digital piano

I've done both input and output, and got sound on both sides.