Damaged circuit board from old Yamaha digital piano, any hope for repair?

Thread Starter

datcid

Joined Jul 4, 2017
6
Hey guys, I was about to attempt a repair of an old Yamaha digital piano however, it ended up getting damaged before I even began (my son was helping me set up this heavy beast and he accidentally screwed the wrong screw into the wrong hole.) Well, of course, the circuit board got damaged as apparently the keyboard didn't have anything to stop it from continuing straight through to the board. Luckily I got this thing for free, but it still sucks.

The piano originally worked perfectly, except that it would freeze/lockup after playing a few notes (usually after about 10 notes, sometimes a few more.) If you turned it off and on it would work again until you pressed another few keys. I figured that it was probably overheating due to a few bad capacitors in the power supply or amplifier, but I never even got a chance to even test them.

Anyways, can you guys please let me know if there is anything that could be done to possibly repair this board? I know it's pretty bad. The model is from 1989, so a replacement board is totally out of the question. I'm not very optimistic, but any ideas/hope would be appreciated ;) I admit that I'm pretty green when it comes to electronics with no formal training, but I'm decent at soldering and have replaced a lot of caps in the past. I have a regular multimeter, but was waiting for an LCR to arrive from china. It looks like I might not have an immediate need anymore :(

Below are a few pics of the damage, the image with the black wire is from the back where the screw came up.back-1.JPG Front-1.JPG Front-2.JPG

Thanks
 
Last edited:

#12

Joined Nov 30, 2010
18,210
I see a crack. I could do that.
You will be soldering little strands of wire across any cracked copper traces and re-melting any pins that intersect with the crack..
You better have some soldering skills! This job is for good eyes and steady hands.
About 40 watts should do it.
 

Papabravo

Joined Feb 24, 2006
13,931
Besides the obvious physical damage there are ageing components and unknown electrical stresses. It also looks like some of the ICs might be past EOL and unobtainable. I think there might be more beneficial pathways to follow. I vote for reverse engineering a schematic, learning the function of the board, and replicating it with modern components. Every techno-wizard needs to do this at least once in a career. I did and it was just about the biggest kick there was at the time.
 

Thread Starter

datcid

Joined Jul 4, 2017
6
Thanks a lot guys, I appreciate the feedback. BTW: forgot to mention, the model is a Yamaha CVP50.

I see a crack. I could do that.
You will be soldering little strands of wire across any cracked copper traces and re-melting any pins that intersect with the crack..
You better have some soldering skills! This job is for good eyes and steady hands.
About 40 watts should do it.
Heh, well, I'll give it a try (after practicing on a few old boards.) I've never attempted to repair tracings before, but I watched a few videos and will research a bit more before attempting. From what I gather, for the wiring I could possibly use a lead wire from a spare led or a single strand from some higher gauge speaker wire? Or is there something more specific that I should be using? It also looks like I might need to use some specialized epoxy to cover the wire once soldered in place? Please forgive my total noobness, but I'm also unclear exactly which affected trace areas that I should be focusing on. How many broken tracks/traces do you guys see? I guess I'll watch a few more tutorials to get a better idea of what exactly to look for.

Couple of cracked tracks and a chipped red capacitor to start with....
Okay, I will definitely replace that cap as well.

Besides the obvious physical damage there are ageing components and unknown electrical stresses. It also looks like some of the ICs might be past EOL and unobtainable. I think there might be more beneficial pathways to follow. I vote for reverse engineering a schematic, learning the function of the board, and replicating it with modern components. Every techno-wizard needs to do this at least once in a career. I did and it was just about the biggest kick there was at the time.
Thanks for the suggestion, but I don't really believe that I have anywhere near the skill required to do something like that at this point in time (since I have basically no electrical background and it is the main board which is like 20" x 14".) I think I'll just take my chances with the track repair and if it doesn't work or other components end up failing, well, no biggie. I also don't really want to put much money into this thing, given that it still also has the problem with randomly locking up after a few notes are played.

Thanks again all
 

#12

Joined Nov 30, 2010
18,210
for the wiring I could possibly use
Use any old P.O.S. you find laying around. The point is that soldering across a crack is like patching drywall across a crack. You must have some fiber in the patch or it will just crack again. In this case, the wire is the fiber and the solder is the drywall mud.
 

Thread Starter

datcid

Joined Jul 4, 2017
6
I see a crack. I could do that.
You will be soldering little strands of wire across any cracked copper traces and re-melting any pins that intersect with the crack..
You better have some soldering skills! This job is for good eyes and steady hands.
About 40 watts should do it.
Okay, I took another picture of the bottom side of the board after moving the black wire and glue that was in the way. I also added some lines showing where I think I will need to do the trace wires, hopefully I've got at least some of the locations right?
 

Attachments

Papabravo

Joined Feb 24, 2006
13,931
...
Thanks for the suggestion, but I don't really believe that I have anywhere near the skill required to do something like that at this point in time (since I have basically no electrical background and it is the main board which is like 20" x 14".) I think I'll just take my chances with the track repair and if it doesn't work or other components end up failing, well, no biggie. I also don't really want to put much money into this thing, given that it still also has the problem with randomly locking up after a few notes are played.
Sorry, I didn't mean to presume facts not in evidence. Put it on your bucket list, the exercise is well worthwhile.
 

Thread Starter

datcid

Joined Jul 4, 2017
6
Sorry, I didn't mean to presume facts not in evidence. Put it on your bucket list, the exercise is well worthwhile.
You had some very valid points and a great idea. I'll definitely keep it on the backburner for some point in the future. At present, I'm just doing online tutorials and introductions to electronics, but I plan to take some official courses within the next year. You've convinced me to keep this board around even if my immediate repairs don't stick :)

I'm really appreciative of the kind folk on this forum with regards to helping beginners. I've tried posting on other electronic forums in the past and the members either totally ignore, discourage or berate new hobbyists.
 

Papabravo

Joined Feb 24, 2006
13,931
You had some very valid points and a great idea. I'll definitely keep it on the backburner for some point in the future. At present, I'm just doing online tutorials and introductions to electronics, but I plan to take some official courses within the next year. You've convinced me to keep this board around even if my immediate repairs don't stick :)

I'm really appreciative of the kind folk on this forum with regards to helping beginners. I've tried posting on other electronic forums in the past and the members either totally ignore, discourage or berate new hobbyists.
We've all walked in your shoes. Many of us when the year had a 196 handle. (FYI Today's year has a 201 handle)
 

absf

Joined Dec 29, 2010
1,947
Here's the block diagram of the CVP50 if it helps your trouble shooting..
cvp50 Block.PNG
I think the main CPU is KPU1. Not sure what are the other 2 CPU used for (HD64180 & HD63c01Y). The 2 GEW chips must be the tone generator for piano and rhythm.

Allen
 

Thread Starter

datcid

Joined Jul 4, 2017
6
Here's the block diagram of the CVP50 if it helps your trouble shooting..
View attachment 130440
I think the main CPU is KPU1. Not sure what are the other 2 CPU used for (HD64180 & HD63c01Y). The 2 GEW chips must be the tone generator for piano and rhythm.

Allen
Thanks Allen, I'm sure this will be very helpful when I get a bit further into the repair. I'm just waiting on a set of tweezers and some flux before attempting my fix on the tracks.
 
If you decide to get rid of the machine, please let me know. I would like to get the circuit boards from a CVP-50 to repair my old CVP-50.


Best Regards,

Andrew Clark
 

narkeleptk

Joined Mar 11, 2019
465
Where better to find people with broken CVP-50 that may want to part with them then a thread talking about the difficulty in repairing one? Seems a good place to me.
 
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