Synthesizer resistors on keys

Thread Starter

hide24

Joined Jul 9, 2019
45
Hi everyone,
I own a synthesizer Alesis Qs 6.2 which some keys don't sound.
I cleaned the rubber contacts, also change new cables and still seems not work. If I use an external Midi keyboard, all the keys sounds with no problem.
I noticed also that on the keys board there are many resistors. What are the purpose of them? Could be some don't work properly and affects the keys? ( I attach a picture)
Thank you very much
 

Attachments

Delta prime

Joined Nov 15, 2019
107
I noticed also that on the keys board there are many resistors. What are the purpose of them?
O' Boy can't tell by the photo but they're not smoked whatever they are?The silk screen shows the symbol for a lot of diodes.What type of solvent did you use to clean the rubber contacts and are they rubber?
I would try searching the number I pulled off the board 02.0181-a 26613330
To see you if you can find a schematic
There's a great troubleshooting section on page 99 or 98 of the manual I hope it helps.
 

Attachments

pmd34

Joined Feb 22, 2014
503
@Delta prime prime has probably got it.. they the lower components in the photo look like diodes for sure, not sure about the long legged ones with bands in the middle however.
The diodes would be used to "multiplex" the keys together in order to reduce the total number of wires needed to connect them up.
 

MrChips

Joined Oct 2, 2009
19,915
If one or two keys do not produce sound I would suspect dirty contacts.
If there are many keys not working, show which keys. This will determine if it is a multiplexing issue.
 

Thread Starter

hide24

Joined Jul 9, 2019
45
Thank you very much for the feedback.

The most strange thing is that the keys don't work by zones.
For example from C1-B1 works, but from C2-G2 not...and like this in several keys.
If its only dirty contact probably would be some randomly keys that don't produce sound, but it's not the case.
Apart from the cables also I replaced the connections to the cables, but still with no succes.
 

Thread Starter

hide24

Joined Jul 9, 2019
45
For clean the contacts I used alcohol mainly of wet tissue paper. But I think it's not the contacts too. Very strange.
 

Dodgydave

Joined Jun 22, 2012
8,674
Thank you very much for the feedback.

The most strange thing is that the keys don't work by zones.
For example from C1-B1 works, but from C2-G2 not...and like this in several keys.
If its only dirty contact probably would be some randomly keys that don't produce sound, but it's not the case.
Apart from the cables also I replaced the connections to the cables, but still with no succes.
That sounds like a multiplex issue, or the PCB associated with that group of notes C2-G2.
 

Thread Starter

hide24

Joined Jul 9, 2019
45
Thank you very much.
What is a multiplex? Sorry I’m very begginer with electronics.
Could be software problem of the synth when send the signal to the keys?
However If I use an external midi keyboard, seems that worked fine.
 

Alec_t

Joined Sep 17, 2013
10,708
The keys are most probably arranged electrically as a matrix of rows and columns and get scanned a row or column at a time by the electronics, i.e the keys are multiplexed. If one of the scan lines is open or short circuit or has gone high resistance then the bunch of keys on that line won't work.
 

MrChips

Joined Oct 2, 2009
19,915
The keys are scanned in a multipexed circuit as shown in the upper right corner.
The drawing is not of high enough resolution to read the print. If you can download the Service Manual that contains the schematics we will be able to trace the connections. Be aware that the Service Manual available without requiring you to register does not have the schematics.

Alesis QS6 Schematics.jpg
 

Thread Starter

hide24

Joined Jul 9, 2019
45
Thank you.
For example, If one of the scan lines is open which is the best way to close it again?
Are we talking about Lines in the Electric board? If I attach a photo of the board is easy to see?
 
Hi everyone,
I own a synthesizer Alesis Qs 6.2 which some keys don't sound.
I cleaned the rubber contacts, also change new cables and still seems not work. If I use an external Midi keyboard, all the keys sounds with no problem.
I noticed also that on the keys board there are many resistors. What are the purpose of them? Could be some don't work properly and affects the keys? ( I attach a picture)
Thank you very much
If all the keys work for an external module, then the keys on your problem keyboard are functioning well.

Do a factory reset. I think you have some zones not going into the internal sound card.
 

Thread Starter

hide24

Joined Jul 9, 2019
45
Sorry, my apologies. I mean I used an external keyboard to control my alesis Qs 6.2, and it sounded all the keys.
 
Sorry, my apologies. I mean I used an external keyboard to control my alesis Qs 6.2, and it sounded all the keys.
Sorry. I misunderstood. It seems as though some range of notes aren't assigned to internal zones possibly. Are the notes missing if you use the alesis as a controller for your other external kb? Again, try a factory reset...worth a shot.
 

Thread Starter

hide24

Joined Jul 9, 2019
45
Thank you.
I cleaned again the contacts and I did also the factory reset.
I tried right now to use the Alesis as a midi controller for my Kawai K4, but the keys don't work.
Also what I notices is the sound sometimes comes and go of some keys.
 
Top