Roland A-90EX All Dead Keys

[bibidily]

I recently picked up a Roland A-90 for a very small trade knowing it had power issues and that the keys were not working.

I was able to fix the power supply issues in about 5 minutes as I have read other threads pointing to 3 DC Power Regulators which often need resoldered. That fixed that problem.

The keys have been more challenging for me to troubleshoot and I would love any tips to point me in the right direction. I am pretty handy with a multi-meter and soldering iron, but am in no way an electrical engineer.

I have put the unit in test mode and have confirmed that all buttons besides the keys, including the Mod/Expression wheels are working and send data. In test mode I have also generated sine waves to test the output of the headphone jack, and stereo 1/4" outs. In test mode not a single key will trigger any sort of velocity data, all are dead. I am pretty confident everything is working except for the dead keys.

I have unplugged, cleaned, and reinserted every ribbon cable going from the keys to the main board. I have tested for continuity a few (not all) of the pins from the ribbon header on the main board to the ribbon header on the keybed board. The few I tested made me feel the ribbon is making solid contact between the boards. I have taken one of the boards of the keybed and inspected the rubber/carbon switches. They visibly look very clean, and I did not proceed to attempt to clean the carbon contacts since all keys are dead.

Any thoughts of what to try or test next? Could all the Carbon contacts need cleaned and that is the cause of the dead keys? I guess I am assuming some of them would still be working if this was the issue?

 

[jmemcse]

Get a schematic. Test points are labeled with a circle with a value in it and an arrow pointing to the test point. Use a digital VOM. This will tell you where the problem is. It might be a component board that you can replace. Who knows. It's a place to start, anyway.

 

[bibidily]

Get a schematic. Test points are labeled with a circle with a value in it and an arrow pointing to the test point. Use a digital VOM. This will tell you where the problem is. It might be a component board that you can replace. Who knows. It's a place to start, anyway.

Thanks, great tip! I am not seeing Circles on the Schematic, but would these triangles be the test points?

 

[Cosmos]

Thanks, great tip! I am not seeing Circles on the Schematic, but would these triangles be the test points?
View attachment 3554

Those triangles are the positive side of the supplies, they feed various parts of other circuitry everywhere you see such a + triangle.

 

[Cosmos]

I recently picked up a Roland A-90 for a very small trade knowing it had power issues and that the keys were not working.

I was able to fix the power supply issues in about 5 minutes as I have read other threads pointing to 3 DC Power Regulators which often need resoldered. That fixed that problem.

The keys have been more challenging for me to troubleshoot and I would love any tips to point me in the right direction. I am pretty handy with a multi-meter and soldering iron, but am in no way an electrical engineer.

I have put the unit in test mode and have confirmed that all buttons besides the keys, including the Mod/Expression wheels are working and send data. In test mode I have also generated sine waves to test the output of the headphone jack, and stereo 1/4" outs. In test mode not a single key will trigger any sort of velocity data, all are dead. I am pretty confident everything is working except for the dead keys.

I have unplugged, cleaned, and reinserted every ribbon cable going from the keys to the main board. I have tested for continuity a few (not all) of the pins from the ribbon header on the main board to the ribbon header on the keybed board. The few I tested made me feel the ribbon is making solid contact between the boards. I have taken one of the boards of the keybed and inspected the rubber/carbon switches. They visibly look very clean, and I did not proceed to attempt to clean the carbon contacts since all keys are dead.

Any thoughts of what to try or test next? Could all the Carbon contacts need cleaned and that is the cause of the dead keys? I guess I am assuming some of them would still be working if this was the issue?

I would check using another keyboard through midi. Connect midi out of another keyboard to midi in of A90 and play other keyboard's keys.
You then could do this vice versa... connect midi out of A90 to midi in of other keyboard and play A90 keys and see if other keyboard plays.

 

[Gourockian]

I would also check to make sure All the voltage regulators are functioning correctly. I once had an issue with my Technics KN 2400 where it switched on as normal, but didn't produce any sound. It turned out to be a dead regulator (-15V, I think) and after replacing it, the keyboard worked perfectly.

 

[bibidily]

Thanks everyone for the help. I got it working. The voltage regulators tested ok, which led me to a loose cable going to the main board. Re-Seating the cable helped with the LCD fading in and out. I found circles on the main board which allowed me to test voltage going to the keybed. Noticed voltage was great at the ribbon connection header but not getting all the way thru the end of the ribbon cable. I snipped a hair of both ends of the ribbon cable and had to apply a bit of force to get them to seat in the headers. Once seated voltage traveled as it should and the keybed came alive. Thanks again!

 

[Cosmos]

Thanks everyone for the help. I got it working. The voltage regulators tested ok, which led me to a loose cable going to the main board. Re-Seating the cable helped with the LCD fading in and out. I found circles on the main board which allowed me to test voltage going to the keybed. Noticed voltage was great at the ribbon connection header but not getting all the way thru the end of the ribbon cable. I snipped a hair of both ends of the ribbon cable and had to apply a bit of force to get them to seat in the headers. Once seated voltage traveled as it should and the keybed came alive. Thanks again!

Good to hear you got it working, well done. The problem with the A90s usually was mechanical, the hammers break at the middle part. Otherwise it's a workhorse not to be missed

 

[Gourockian]

Good news! Thanks for letting us know the cause and solution.

 

[delaware dave]

In your OP you wrote this: "..I have unplugged, cleaned, and reinserted every ribbon cable going from the keys to the main board. I have tested for continuity a few (not all) of the pins from the ribbon header on the main board to the ribbon header on the keybed board. The few I tested made me feel the ribbon is making solid contact between .."

Then you wrote this: ".. which led me to a loose cable going to the main board.."

Not sure where im going with this post so i guess ill just stop here.