Roland U-20 keybed in a Roland JD-800


I bought another JD-800 about a year ago. First owner, didn’t use it a lot and it came with ALL THE CARDS (yes, including the String Ensemble cards). And it looked absolutely MINT.

Well okay, small problem: the keys where a mess. Red glue everywhere and worse: he had taken it to ‘a guy’ who fixed it. Sort of… No, he made matters worse actually.

When I opened it up I noticed a few missing screws. No problem. I removed the keys.. first problem: instead of just removing the red glue with sodium hydroxide the red glue was scraped off with a knife and the rest was covered with some kind of transparent glue. Messy. There was red glue everywhere. The green flex pcb was covered in it. The metal frame that holds the keys was basically glued to the metal chassis of the JD-800. It required force to come of.

Second problem: the green flex PCB was damaged underneath one key and a repair effort was made:

IMG_20200404_153923 (Medium)

No surprise: this key didn’t work.

The rest of the mess:

I cleaned it up as best as I could and put the keybed back in the synth without the keys. I switched it on to test the keys (you can just press the rubber domes). About 8 keys didn’t work. I cleaned the contacts several times but they remained dead. Bummer. They where all random keys and there was no pattern so I didn’t really know what caused them not to work.

Now what….

The green flex pcb is in a bad state and this part can’t be bought new. Because it is a flexible circuitboard you can’t really solder cracked traces (although I fixed 2 bad traces on my other JD-800 with great success using something called Wire Glue)

Even I if find the problems causing the 8 keys not functioning and fix it I didn’t think I could fix the one key in the first picture where the pads where badly damaged. And having a JD-800 with one key somewhere in the center of the keybed that doesn’t work just isn’t acceptable.

There is one solution: Find a Roland U-20 (or D-5 i think..) and use that keybed. They are almost identical. And almost means: there is a pretty big problem standing in the way of success.

The green flex pcb’s on the JD-800, U-20 (and D-5) are identical. The problem is the flex cable connecting the green pcb to the mainboard of the instrument. They are very different. So you can’t drop a U-20 keybed in a JD-800 and hook it up. I had to find a donor first so the JD-800 was parked in a corner for a while (well the better part of a year actually πŸ™‚ ) Until someone gave me perfectly working U-20 keybed. Thanks Rob!

This was parked next to the JD-800 for a month or 2 until today when I decided I wanted to give this a go.

I had one solution in mind and that was to somehow try and remove the flex cable from the U-20 keybed and 3D print this part.

Pretty nifty idea. You just put 24 metal wires through it and bolt it on the metal chassis. Now you can solder a flat cable to the 24 wires sticking out of it and solder the other end of the flat cable the the little pcb on the bottom of the metal frame. Not exactly an OEM solution but when there are no parts available..

About a month ago I bought a Roland GW-7 which has display problems:

I fixed this by applying heat (at 180 Celsius) with a soldering iron and some baking paper to fix the broken connections in the flex ribbon cable. Worked 100%.

Why not try and replace the 2 ribbon cables of the U-20 and JD-800? I took the U-20 keybed and grabbed my soldering iron.

This was actually pretty easy. Only a few minutes of work and the ribbon cable was disconnected. Make sure you always have a finger somewhere on the ribbon cable because when it’s disconnected for say about 75% the force on the cable (it wants to move in an upwards direction because there is tension on it) can rip the remaining 25% of the contacts of the pcb. I set my soldering iron to 180 Celsius and gently worked my way from left to right. I used the Stanley knife to help start the separation where the rivet goes on the left. When the first 5mm where detached the knife was no longer needed. It’s a very delicate connector. Just be carefull πŸ™‚ I came off with hardly any damage as you can see.

Next the JD-800 keybed:

This one also came off without problems and hardly any damage. Great!

I then switched the U-20 green pcb to the JD-800 frame (after cleaning everything). Now the challenge to reattach the blue JD-800 flat cable to the green U-20 flex circuit and make all 24 traces work… I aligned everything and put the rubber contacts for the first octave on the frame to secure the green pcb and got to work.

Here are the images of the repair and my professional repair kitchen table studio πŸ™‚

I held the connector in place with 2 clamps and fired up the soldering iron. A few minutes later everything was attached solid again. I triple checked everything and put the plastic retainer and the 2 black plastic rivets back. Looks great but will it work? I cleaned and installed the other 4 rubber contact strips and put the keybed in the JD-800 (without the keys). Switched it on and put on some headphones……











Yeah baby! Now all I need to do is clean the keys and a few other minor issues and I have a mint JD-800 πŸ™‚









5 thoughts on “Roland U-20 keybed in a Roland JD-800

  1. I’m repairing a Roland EP3 that has suffered the same failure of the joint between the 2 flexi PCBs; I want to try the method you tried with the 3D printed block; did you have to cut away the metal beneath where the block is located or is the flexi board wrapped around the edge of the metalwork as it was originally?


    1. Hi Martin,

      There is no need to cut away any metal. Just place the 3d printed part on top of the original flex pcb and solder the wires to the pcb on the bottom of the keybed. Both my JD-800’s are currently having keybed issues though.. There is a guy in the UK who is designing (and hopefully producing) replacement pcb’s for the JD-800. If and when they are available I will immediately buy 2 to hopefully permanently fix my JD-800’s.

      This is the link to his page:–LQad7Mww76IYtwbEAtTBtwTpgNpeEKYrrs

      regards, Jorick

      Liked by 1 person

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