Beto-Music wrote:Thanks Jcitron
One white key got a deep crack near the pivolt point. What glue should I use? Superglue? Is it wise to glue it before put in place, let dry after connect and add another layer of glue after dried?
The rubbers look ok. The cell phone technician for micro circuit repair said that apply a resin over the fixed area for protection, and use 0,1mm copper. I presume it's better than use tin allow soldering to trace lines. He can't check here in my roland F-90 in my home, but can check if current pass in her repaired line, using a multimeter.
Roland of Brazil was a mess, of little help. They just sent me a link for authorized technical suport bussiness on my state. I contacted one but this one recommended me another Roland authorized technical bussines for buy new pieces. I will talk with the reponsible guy tomorrow. Let's see if they have better price for the new set (with rubber strip together).
I'm considering the possibility of buy a new set like you said.
I was thinkig about let the micro circuit technician repair just one PCB, and test it, to see if works, and then if fine let hin fix the others. What PCB do you recommend me to sellect for this test?
Center, left or right should I choose?
Is that possible to a circuit line deffect in one PCB affect the keys of the other PCB, since the PCB bellow keys are connected one to another?
jcitron wrote:Wow! I've been following this thread since the beginning. As a now long retired electronics technician, my recommendation is to replace the boards if you can.
I don't know what plastic they use. Talk to the Roland tech, or another piano technician about the key. They should recommend the kind of glue needed. The problem is if the wrong glue is used, it will either not stick at all, which is a good thing, or worse it could melt the plastic and destroy the key completely. I had that occur with something else, not a piano key, and i ruined the item with the glue which turned everything into mush.
Your PCB technician is doing it the right way. The epoxy or resin over the repaired areas will prevent things from landing on the surface and shorting out the connections. In my old days as a tech, we would use some green gloopy stuff for that. I don't remember what it was called, but it looked similar to the stuff on the circuit boards I repaired. This may be because this was a commercial product and the company wanted the boards to look right.
It is possible for things to not work inside the circuit board. Let me explain. The circuit boards are no longer single-sided, meaning like the very olden days circuits were only on one side with the components pushed through and soldered to the pads. This is still used for simple things, but for more complex circuits, such as computer motherboards and digital pianos, they need to fit a lot more circuits in a smaller space. What this means is there are circuits inside the board as was well as on the surface, and on top of that, there are layers upon layers of circuit paths all over. Multilayer boards can be a few mm thick with various traces going every which way as needed.
The problem is when there's a crack or pull, there's a possibility that the crack has affected more than the top-most or surface circuits. I have seen multilayer boards with no apparent problem, but due to flexing the board inside the computer case, very fine cracks occurred on the inside of the layers causing weird things to happen such as intermittent failures. With ripped circuits, it's possible that the interconnections between the layers is damaged when an upper layer is torn. Remember, these circuits are only 1/2 mm thick if that and are very delicate.
With that said, I would as you say here talk to the Roland tech about this. He can recommend what to do, hopefully with this and the broken key. I wish you a lot of luck with this.
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