Baffling Midi Problem

[Roddy]

I have a midi problem with my accordion which has everyone baffled.

I have a 72 bass Fantini piano accordion. Approximately 10 years ago I had a Limex full midi system installed with the sound card fitted inside the accordion. It worked fine for a year or so then it began misbehaving. It would change patterns and key at random making the midi unplayable. My midi installer, after several attempts to repair it decided that the sound card was not suited to being inside the accordion, the space being too small, and fitted it into an external case. Everything was fine until last year when once again, at random the midi would change key, patterns and sometimes transpose as I was playing.

The original installer has gone out of business but I found another midi expert not too far away and took it to him to repair. The cause of the problem has not be identified. Over the last 6 months the old Limex midi system was ripped out and a complete new system fitted. The problem returned after a couple of days of playing so new sound module, V3 was bought to replace the Limex sound module but again after a few hours of playing the problem reoccurs. The problem is intermittent. It might be fine one day then unplayable the next. When the problems occurs and the accordion is resting, I.e. not being played, every few seconds a random note sounds. A signal obviously being sent from the accordion to trigger the sound module.

The problem must be with the accordion set up as the issues occur with different sound modules but we cannot identify what is causing it. Any suggestions please my repairer has never come across this problem before. The fact that it occurs randomly doesn't help tracing the problem.

 

[Giovanni]

I have a midi problem with my accordion which has everyone baffled.

I have a 72 bass Fantini piano accordion. Approximately 10 years ago I had a Limex full midi system installed with the sound card fitted inside the accordion. It worked fine for a year or so then it began misbehaving. It would change patterns and key at random making the midi unplayable. My midi installer, after several attempts to repair it decided that the sound card was not suited to being inside the accordion, the space being too small, and fitted it into an external case. Everything was fine until last year when once again, at random the midi would change key, patterns and sometimes transpose as I was playing.

The original installer has gone out of business but I found another midi expert not too far away and took it to him to repair. The cause of the problem has not be identified. Over the last 6 months the old Limex midi system was ripped out and a complete new system fitted. The problem returned after a couple of days of playing so new sound module, V3 was bought to replace the Limex sound module but again after a few hours of playing the problem reoccurs. The problem is intermittent. It might be fine one day then unplayable the next. When the problems occurs and the accordion is resting, I.e. not being played, every few seconds a random note sounds. A signal obviously being sent from the accordion to trigger the sound module.

The problem must be with the accordion set up as the issues occur with different sound modules but we cannot identify what is causing it. Any suggestions please my repairer has never come across this problem before. The fact that it occurs randomly doesn't help tracing the problem.

Have you tried making contact with Limex direct to their technical dept ???

 

[Ventura]

it seems likely to me, from what you have said, that
actually the entire Limex system was NOT ripped out
6 months ago

the only possible cause of this problem, which has happened
under 3 different conditions, is the one factor common to all

think about it, removing the sound engine into an external
box obviously provided the repair by relieving physical pressure
and/or cleaning the contacts and connectors still inside the accordion

then the same problem recurred after some years, suggesting
the original problem was only "fixed" by luck

now a brand new Limex has been installed, but clearly a shortcut
was taken, and the second tech used the existing keyswitching system,
and perhaps the switching matrix as well (a sub-board directly
associated with the keyswitches, and there is where the problem
actually will be found.. a stray pressure that causes a board
connector to have poor contract, a flat cable that has been
scratched, a socketed chip that is tugged by a stray piece of wiring

in other words, the only thing that could be causing this problem
is that which is common to all 3 situations.. the switching system
and logic circuitry onboard the accordion from the original
installation, and WAS LEFT IN THERE

there is zero to infinitesimal chance that the exact same rare problem
would manifest itself in two entirely independent and totally different
LIMEX installs for the same person.. i might believe it if it
happened to you and to another fella in Seattle or Nome Alaska

have a talk with your new tech and tell him he has been caught..
now he has to finish the job for real, remove and replace the
hardware and control circuitry from the switches on out

 

[Roddy]

it seems likely to me, from what you have said, that
actually the entire Limex system was NOT ripped out
6 months ago

the only possible cause of this problem, which has happened
under 3 different conditions, is the one factor common to all

think about it, removing the sound engine into an external
box obviously provided the repair by relieving physical pressure
and/or cleaning the contacts and connectors still inside the accordion

then the same problem recurred after some years, suggesting
the original problem was only "fixed" by luck

now a brand new Limex has been installed, but clearly a shortcut
was taken, and the second tech used the existing keyswitching system,
and perhaps the switching matrix as well (a sub-board directly
associated with the keyswitches, and there is where the problem
actually will be found.. a stray pressure that causes a board
connector to have poor contract, a flat cable that has been
scratched, a socketed chip that is tugged by a stray piece of wiring

in other words, the only thing that could be causing this problem
is that which is common to all 3 situations.. the switching system
and logic circuitry onboard the accordion from the original
installation, and WAS LEFT IN THERE

there is zero to infinitesimal chance that the exact same rare problem
would manifest itself in two entirely independent and totally different
LIMEX installs for the same person.. i might believe it if it
happened to you and to another fella in Seattle or Nome Alaska

have a talk with your new tech and tell him he has been caught..
now he has to finish the job for real, remove and replace the
hardware and control circuitry from the switches on out

Thanks for the suggestion. I’ll see him next week.

 

[SteveBox]

I have a Limex MIDI system, but have never had problems like this. Knowing how the key scanning works, I would suspect an intermittent bad connection within the cable that passes through the accordion or in the connectors for the cable. Limex uses analog hall effect sensors on the keys, which generate a variable voltage proportional to the distance between the sensor and a magnet attached to the pallet lever. The main computer measures these voltages to determine what keys are at rest, which are partially depressed, and which are fully depressed. It measures this voltage for each sensor hundreds of times a second and can calculate a MIDI velocity value by measuring the time it takes a key to go from rest to fully depressed.

The outputs of all of the analog hall effect sensors are connected together to a common analog signal line that runs from the right-hand side of the accordion, through the bellows, to the main computer board on the left-hand side. Of course, this design could never work if all of the sensors were on all of the time, but they are not. Digital circuitry turns on only one sensor at a time, each one being turned on, then off about 300 times a second. Measuring the changing voltage on this analog line as each sensor takes a turn being on is very critical to determining the MIDI data. If there is a loose connection, broken wire, corroded contact, etc. anywhere on this analog signal line, it would cause errors in the MIDI data. A loose connection on one of the digital control lines that control switching the hall effect sensors on and off would also cause errors in the MIDI data.

 

[Ventura]

The outputs of all of the analog hall effect sensors are connected together to a common analog signal line that runs from the right-hand side of the accordion, through the bellows, to the main computer board on the left-hand side.

great info..

 

[KeysFla]

You might want to look at this article. I am not sure if this helps but some kind of a midi loop could cause problems. I did have a problem on my new Korg arranger where sounds were being changed…in my case I had a widi bud in the usb port and forgot I had a widi master in the midi ports. For some reason they paired…creating a midi loop.

https://support.sequential.com/hc/en-gb/articles/12826311546642-Troubleshooting-MIDI-Feedback-Loops#:~:text=One%20easy%20solution%20is%20to,MIDI%20input%20on%20the%20synth.

 

[Morgan28]

This sounds like a grounding or electrical interference issue. Check this few things to help out.

Loose/damaged wiring – Especially near the bass buttons or bellows movement.
Static buildup – Try anti-static spray on bellows or a grounding strap.
Faulty sensors – If capacitive, humidity/temperature changes may trigger false signals.
Power supply – Ensure stable voltage to the MIDI system.

Test in different environments to rule out external interference. If possible, bypass internal wiring temporarily to isolate the fault.

 

[Roddy]

Thanks for the suggestions. I’ll pass ithem on to the installer. It’s back with him again, The difficulty is that the problems cannot be reproduced to order. It is so random. I have played for days on end trying to make it misbehave and it is perfect. Then sod’s Law I take it to a gig and it is unplayable.