Recently purchased 1989 CVP-50 played fine for several days after being brought home, then stopped producing any audio, niether in response to piano keys, accompaniment, nor rhythm selections. Speakers now only produce barely audible white noise whose level is unaffected by volume slide control. White noise cuts out when headphones are jacked-in but is not reproduced on headphones. Headphones do produce loud pops coinciding to relays on audio board kicking in and out on power-up and power-down. Hooked up RCA audio output jacks at piano rear to aux input of Bose speaker and got no sound. I suspect a fault in the amplifier assembly, either in the audio board (Syntaur Item 6560) or the power supply/amp (Syntaur Item 6561). These Items appear to be identical parts from a CVP-20 currently in Syntaur’s inventory, judging by comparison to the these photos from my CVP-50: https://photos.app.goo.gl/uGsZQ9uMWzgvm8RC6
Seeking feedback from the Synth repair forum regarding a recommended course of action. Are the symptoms I describe consistent with a failure in the amp? Are there any simple tests I can do with a multimeter to confirm my amp is bad before commiting to buying a replacement? I’d appreciate any advice you can offer.
We don’t have service info on the CVP-50, but I’m guessing that these boards will have different Yamaha part numbers between the CVP-50 and CVP-20. In your photos, you can see that the boards have several model numbers screened onto them, including the 50 and the 20, but only CVP-50 is marked. This means that several models use that same printed circuit board, but that it is populated differently for each of them. So that board may not have a certain connector for one model, when it is there for another model. Or the power amp ICs might be different ratings, or one section of electronics may be left out, etc.
So while you might get lucky using a CVP-20 board, you might also get unlucky. Unfortunately, we don’t have a way to tell you which answer that might be…
As a diagnostic approach, if the keyboard acts normal, other than not producing sound, you can look for a signal at the audio board. If you can find a signal going in, then you can trace it and see where it fails - maybe an op amp is bad. Doing this requires an oscilloscope and a schematic, though - so it’s probably a job for a service center.
Thanks for your reply. I’ve was able to download the service manuals for both the CVP-50 and -20 models and verify that the PU60P audio boards are populated with the same components and connectors, while the PU60M power amp boards differ only by the presence of 2 air core coils found on the CVP-20 that are absent on the CVP-50 board. Since I was planning on replacing both boards at the same, I think the risk is minimal that the CVP-20 boards won’t provide the same functionality. I’ll assume the risk and order the boards.
Just a follow up to let you know that swapping out the power amp board did the trick. Sound is restored! Thanks Syntaur for the advice and having the part in stock. Keep up the good work!