I have a Roland D5, which I use as a slave keyboard, and half a dozen of the keys (all adjacent) have stopped working. My computer tells me that there is no MIDI message coming from them, but the sound generation unit is still working for those notes. I've had it apart and it looks a bit gungy in there (and difficult to pull the keys apart!). Can anybody tell me if it is likley that the fault is mechanical or electrical, and has anyone else had this problem and fixed it ? Cheers. Andy.

Andy,

I acctualy don't know this model Roland D5, but most of recent keyboards, including Roland and Ensoniq uses a micro processor to scan the keyboard.

This process uses a diode matrix connected to the keyboard to lessen the number of inputs and usually have 12 rows representing the keys from A to G, including half tones, and a number of columns representing the octaves, which changes according with the model of keyboard (the number of octaves on it). Each row and column are connected to the micro processor to identify the note(s) pressed. The scan rate is fast enough to detect a chord in different time identifying each note individualy.

So, if you press a C3, for example, the output of the matrix will be row "C", colum 3 and the note will be identified.

As you noted that the synth still sounds for that notes receiving MIDI commands, I can conclude that your sound chip is perfect and the probably cause of the malfunction is just one burned diode (or cold soldering) of that matrix, that represents one octave.

Are the missing keys on the edge of the keyboard? This would explains easily why you have only 6 missing notes and not a complete octave, cause the notes belongs to a not completed octave. The other alternative may be that Roland use one diode for each half octave, but I don't believe so.

Good news! This electrical problem is very simple to be detected by a conventional multimeter and be replaced or resoldered by any qualified eletronical technician.

Regards and good luck.
Fernando

The scan is performed with to lines for each key, and then the timedifference between the exitation gives the velocity.
I had a some keys on my D50 that didn't respond and some that always had velocity 100, so i removed the dirt under the rubberpads. If that doesn't fix all the keys then you could tyr to replace the rubberpads they are not that expensive. I've had this problem many times with the D50 so it wouldn't be a surprice if it also happens for a D5

I have had problems with my juno2 and w30 where odd keys stop working and it was dust under the rubber contacts .oh yeah and a punter spilt his bourbon dowm my A50 and took out about 16 notes ,which came right after a clean (bit annoying when you're out of town though damn it).Unless you've had a spillage i cant really see dust or dirt being your problem,still it wont hurt to give it a clean
you never know

Another thing to check would be the ribbon connectors coming from the keyboard. There should be one for each "scan set" of keys, and sometimes these can wiggle off the connector a little, it may not be that visible but enough to break an electrical connection.

Try reseating each of the connectors first before you have surgery performed.

I've never had this problem, but I've read about it happening to lots of keyboards.

I had also the problem with my D-50 that one key had max velocity, and I fixed it by cleaning the contact. I have also a problem with the After Touch controller. It doesn't work, and I didn't find anything wrong inside the synth. Does somebody know how the aftertouch work?