My (previously parents') Yamaha Clavinova CVP-8 must be 25 years old now. It had been getting into the habit of cutting out after it'd been on a while: all the lights would go off and the buttons would be unresponsive, there'd be no sound from the keys but a gentle background buzz from the speakers.
If you turned it off and on again immediately then you'd get a gentle pop and all the same non-working symptoms, but if you left it off for a bit it tended to start working again, presumably as it cooled down. However after a while it stopped the "starting working" again and was basically broken.
[Make sure you know how to be safe with mains electronics before you go doing this - there are dangerous voltages inside.]
Opening up the lid was a case of four screws on the underside, but the two at the rear are inaccessible while it's properly mounted on the stand just to make things more difficult.
Anyway, I'd found the power supply board with the big capacitors on it and I'd replaced those because I know that caps are often the thing that go bad in old electronics. Unfortunately, this made no difference (though the piano did briefly start working again just to throw me off the scent). FYI: The big cap in the bottom right of the board was charged to 20v and retained that voltage for at least a couple of days - nice big spark when I shorted it (so use a resistor)!
However, after another session of fiddling and some lucky turning on and off of the piano I worked out that my issue seemed to be that when it was working the machine had 2v or 4v (I think it was AC) measurable at (both sides of) the fuse towards the rear (using the metal heatsink case of that board as ground), and when it wasn't working it had 0v. I traced the track on the underside of the PCB back to one of the end pins of the connector on the RHS of board - this was a wire directly from the big transformer, so I figured either the transformer was broken or... did that solder joint look slightly less than perfect through a magnifying class? Turned out it was! I resoldered all the joints on the bottom of the (what was it, 7 or 8 pin) connector and my Clavinova is working again!
PS Credit to Yamaha for building a piece of kit that lasts this long.
(Other notes: The rectifier near the connector gives out about 20v on the rear-right and the front-left pins. I measure the cap of the (now replaced) big capacitor at the bottom right of the board and it was at 20v while the machine was on. However, the identical big cap next to it (by its "cap") was at 0v - not sure what that's about. Off to the left two of the other 3 or 4 bigger caps were at 8v and 6v and the other two were 0v, I think.)
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Hi I know this is a old thread but did it cure it over long term. Kind regards Scott
Excellent news. (Unless you were looking for an excuse to buy a new piano, in which case... sorry!)
Would you believe o had the EXACT same problem. Same keyboard. Same symptoms. Popped her open , checked the fuses, and resoldered the connections on the pin going to the transistor. And viola! We have music. Can’t thank you enough. This was amazing
Two other people in the world? We're on a roll!
Maybe you've given me the nudge I need to finally try to open up the difficult-looking keyboard section and do something about the 3 or 4 keys that have clicked for 20 years. Or... nah, they're not *that* loud.
Cheers.
Gotta love an old thread. I just picked a CVP-8 up for free having a similar issue. All torn down. Off to get fuses and some bits. I'm feeling good about the odds.
Cheers
https://elektrotanya.com/yamaha_cvp-8.zip/download.html
Service Manual includes schematic in seperate pdf for anyone else who comes through.
Good luck.
FYI, a month or two ago I finally got fed up with all the sticking, clicking keys and stripped the CVP-8 down enough to get to the keyboard unit.
I spent a lot of the weekend popping out springs and keys, cleaning the sticky gunk off the kdy-sides with isopropyl alcohol and putting them back in (but swapping the keys just above middle-C with with the lesser used ones in the top octaves and those below middle-C with those in the lowest octaves).
The little metal springs themselves seem surprisingly okay and swapping those around had little effect on how well the keys spring back. I think over the years the spring wears its way into the plastic where it sits in the corner of the keys - it's effectively compressed slightly less when it's in place and therefore provides less return force. I used a little bit of Bondic in some of the keys which still didn't return properly, just to fill in that tiny gap by a millimetre or so. (Bondic is the wrong material really but it's what I had handy and gives a chance to get the amount / location right before you make it set. Might try Whitemorph next time!) Didn't take long for some of the keys to start slowing down again but the whole thing is way better than it was before.
Unfortunately, it seems that the sensors under a couple of the keys (middle C and maybe the G above) are now unreliable which causes a weird audio glitch in the way they play and the sustain of other notes that are down at the time I play them.
Still, it's got me through lockdown and social distancing and if the keyboard doesn't have a fault then I'll have to blame my playing...
Just jumping on this old thread.....i have a cvp-8 which has died but there's not power coming out of the transformer other than the 4v line. I don't suppose anyone knows where I can get a replacement transformer? Hell of a long shot!!
Not unless it's this one!
https://www.ebay.co.uk/itm/Yamaha-Clavinova-Original-Replacement-Part-Power-Transformer-XJ982/183923268290?hash=item2ad2ae5ac2:g:UJoAAOSwbe1dWXxt
But you're just on a random blog post here. You might do better heading over to http://forum.pianoworld.com/ , say.
Cheers.
Thanks for the reply. I fixed the bugger! Turns out I was being an idiot to start with (it's many many years since I did electronics). I was measuring the transformer output with the multimeter set to DC (bangs head).
Anyway, using the schematic from this thread I identified that the 5v output was dead from one of the voltage regulators. Turns out that that badger had a crap solder joint on one leg. Quick bit of heat and it's working again! Happy days. Thanks all.
And just like that, there goes your excuse to buy a new one. Well done anyway!
(My middle C and G (above - 4 is it?) sensors seem to be flaky now. Just need a few more... :-) )
I've actually rescued this one from the dump, someone was going to chuck it so I'm very happy to get it working. I've totally stripped the keyboard now, cleaning everything....just ordered some proper lubricant. Hopefully I'll remember how it all goes back together!
Had same problem and now fixed. Even ROM books are working again. Thank you
Excellent! (Mine's playing up again - either my soldering was woeful or I've got some new bad joints...)
Hi Aaargh, thanks for your helpful account all that time ago. It directed me to the T2A fuse that had blown. I’m hoping you’re still picking up messages as I’m after some advice about the keys out to clean. I’ve taken all screws out from underneath and the six or so small screws at the back end. But then it’s the white wires that feed from underneath the keyboard, through the holes and into the circuit board. How do these disconnect? They are very taught as it is so I do t think I can angle the keyboard up to look for a way to release from underneath without snapping them. Any help greatly appreciated. Thanks
According to an old photo I just found, if you're talking about the 28 or so wires in a line that go into the circuit board just above the Eb-above-middle-C, then that's a connector (or maybe two) on the *circuit-board* end.
Can't see the exact details in the photo but it's probably slightly latching - you'll probably want a small screwdriver to gently flex one side (the back one?) over a little tab or two - but then you'll be able to unplug the wires from the circuit board.
Cheers.
That’s good of you to get back, I’ll give it a go. Hopefully getting the individual keys out will be straightforward. The YouTube videos for more modern Clavinova key removal don’t apply to this model. Have you kept yours going? Thanks again
See https://computer-aaaargh.blogspot.com/2023/07/yamaha-cvp-8-some-disassembly-photos.html
Oh - and here's some fella's youtube video for what looks like the right keyboard mechanism: https://www.youtube.com/watch?v=1KuzgXSS1kA
That’s great. Thank you. I got some time on it this weekend, I’m about half way through the keyboard, the whites are coming up fine with some cleaning, but the black keys aren’t. A few of them I suspect are rubbing on the rubber posts. What lubricant did you use for these, and also did you lubricate the mechanism that the keys sit in, maybe at the pivot point, after wiping the old gunk off? Thanks again for your help.
Hi again aaargh. Just to let you know it’s all fine and dusted. I used Molykote 44 grease which a few on the web had said they used, and it all is much better. Thanks again for your ancient post about the fuse block, I never would have been able to diagnose that my fuse had gone without you describing the exact same symptoms. All the best.
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