HELP I got an old Accordion with Midi interface

[blaze_01]

I got an old accordion from the 70's/80's with midi.

The midi is installed later and uses a 5pin connection (only 3 pins has wires inside: Shield/power/data)

I wanted to get this to work, inside FL studio, but cant get it work.

Im using a USB-MIDI cable, and it seems i cant even get any software to register buttons at all.


The instrument has installed a small display and 8 buttons, where the display is supposed to show numbers.

However the display doesnt even turn on, and the cable is showing a light for "Power", but no light for in/out

I tried to scroll through channels inside the FL studio output section, when i have the usb driver chosen,
and the blue "out" light on the cable flashes quickly and goes dim.

I cant get the green light (IN) to flash or light at all.

The midi interface just says "RMS-MIDI" and nothing more.

Any ideas on how i can get this working, would be super fun.

 

[SeaGtGruff]

It sounds like the instrument has other problems than with just the MIDI, such as with the display. If that is in fact the case, then you would probably need to get the instrument fixed before you can use it for MIDI.

However, if you want to double check whether any MIDI data is coming from the instrument, you could use a MIDI monitor such as MIDI-OX to see what MIDI messages are being sent from the instrument. Even an "idle" MIDI device will normally be sending a continuous stream of MIDI messages, such as "Active Sensing" messages interspersed between several "Timing Clock" messages.

Note that FL Studio might include a MIDI monitor function; but I'm not conversant with FL Studio, so I don't know if it does. And if you use MIDI-OX, you should be sure to check the options to be sure all message types are being displayed in the monitor window, otherwise you might be getting a steady stream of messages even though it appears as though nothing is being received.

 

[blaze_01]

Thanks for reply.
I already inspected the instrument to check for shorts, loose cables etc.
I know these things usually came with external sound modules that also had a external power supply.
Could i possibly need more power or should a basic usb-midi be enough?

I already tried the midi software, im not entirely sure how to use it, but after setting up the inputs in settings, the instrument were shown red. No response.

 

[SeaGtGruff]

Does the accordion have a place to plug in a power cable?

 

[blaze_01]

I was looking for that but no.
I found only 1 midi socket.
Would i plug out or in on the cable into that socket?

I inspected the behind the socket.
3 wires. Red brown yellow.
The 3 wires goes to a tiny circuit board. From there, ot goes to the tiny display and to all the buttons inside the instrument.

It seems like its only powered from the midi.


I started woundering if old midis from the 80s-90s needed something more than just plugnplay into a modern combuter.

I gonna take my multimeter and see how much voltage the cable supply when plugged in.
Measured from the inside of the instrument.

 

[tjw]

MIDI cannot transfer power to the instrument. It's a signal connection only. This is true even of modern-day MIDI. It's unlike USB, which can supply power as well as signal.

If you don't see another connector, perhaps it's battery-powered ?

 

[happyrat1]

First of all, MIDI OUT always connects to MIDI IN and vice versa.

Secondly, the MIDI Spec is a low power current loop.

Definitely not enough to power a CPU and display on it's own.

The MIDI Interface built into the accordion definitely requires some sort of power source aside from the MIDI interface be it wall wart or an internal battery.

Here's a tutorial on the electrical aspects of the MIDI spec.

MIDI Tutorial - SparkFun Learn

As for the MIDI interface built into your accordion? Check for an internal battery holder, probably a 9V type.

Gary .

 

[blaze_01]

Thanks!
I think you are right. After following every wire inside and searching for any battery or power source, im lost. I cant find anything of the sort.

Now after i found this in the picture, and also there is a display in the front, i belive so too that this would need power. And i cant seem to figure out

I read through the link.
And googled some, and found out the pin for voltage on the midi is supposed to be 5v?
I however measured it and got 0.1-0.35v

I dont know. Im just feeling more lost now.

I guess my last attempt woyld be to completly disassemble the unit in the front with the small display and look for a clock battery or something hehe.

 

[blaze_01]

 

[happyrat1]

What's the chip number of the large chip on there? You could google the pinout and see what the operating voltage and Vcc pin number is and that would give you an idea.

It's probably a CMOS chip with an operating range of between 5 and 15 VDC.

Pay attention to the white wire connected to the end of the board as well as the Yellow with Brown Stripes Wire. These are very likely Ground and Vcc.

Search everywhere on the accordion for a likely place to hide a 9V battery connector. Since it looks like a custom retrofit, the battery could have been hidden away almost anywhere.

Gary

 

[happyrat1]

Also track back the wires from the 4 pin header in the top of the photo. These are also likely suspects of power supply wires.

Gary

 

[happyrat1]

If it was indeed powered by a 9v battery then it is likely that the battery compartment would have had to be accessible by the end user.

Or look around for a 3.5 mm phone jack somewhere on the unit to plug in a power supply.

Gary

 

[happyrat1]

The solid green, yellow, and brown wires on the 4 pin header probably lead back to the voltage regulator that supplies the whole thing.

Gary

 

[happyrat1]

BTW, the bottom two headers with all the wires are probably connected to the keyboard scanning matrix inside the accordion. We can safely ignore all those wires for now.

Gary

 

[blaze_01]

hi again.
i just asked aroundfor someone with the same brand of aftermarket midi.
they say its powered by 5v, through the midi cable.

I decided to have a look inside my cheap, midicable to find only two wires actually were connected, where the "shield" wire was cut off.

I just ordered a good brand "M-audio" midi to usb, and gonna have a try when it arrives.

 

[happyrat1]

Why not just wire in a 5 V DC supply to the connector with a diode to prevent back current reaching the computer?

In theory it should work and the USB standard is very limited in how much 5VDC current is can supply to a circuit.

Unless you get a USB 3.0 device.

Gary

 

[tjw]

Only two wires carry the MIDI signal. It is a "current-loop". The shield wire does not participate in the signal connection, in fact, it is probably intentionally disconnected to prevent unintended signal participation.

It is usually not desirable to connect a shield at both ends of a cable run. If the shield can carry current, then it can re-radiate extraneous signal interference to the wires inside it. Disconnecting It can also avoid ground-loops which create offset voltages appearing in series with the signal. These ground-loops usually present as "hum" from environmental 50 or 60 Hertz power wiring. In some instances, the ground-loop can include ground wires of the power wiring.

 

[blaze_01]

If the shield pin usually is not connected then im in trouble.
After a good look inside the instrument i can for sure see the "shield" cable inside, is 100% brown ground cable.
If the midi cable doesnt provide a ground through the shieldpin, my accordion will never power up using this way.

However i got some news.

My m-audio Uno arrived today (usbtomidi cable)
And it def provides a 5v supply at both pins to the sides of the middle top pin (shield)
The old chinese knockoff cable didnt.

So at least im one step closer now.
However, it wouldnt power up the instrument

So i did some experimentig inside:

Straight from the cable that says (to midi in) provides current.
The other cable that says (to midi out) does not provide current, maybe like 0.5v.


Now i plugged it in the accordion and measured inside, right behind the pins in the input.
It will NOT power up, but i noticed a 1v drop down to 4v inside.
After googling one of the smaller chips inside and found a sheet, i saw the chip needed 5v max and 4.5v min.
So if i drop to 4v, that wouldnt even be enough for the chips inside to work.

I can only wounder why this happends.

An accordion group on facebook said these midi interfaces came with some extra equipment.

From the accordion to a "box" which had a powersupply of 5v.
Then from the box to a sound module which had its own powersupply.

Now this shouldnt be a problem as i basically use my usb to provide power.

 

[blaze_01]

In the picture above you can see how it works.
When i push a button, the tiny magnet on the rod are lifted up and away from the electrical component.
I measure this thing too to 1.5v.
Between the two pins on each side.
The middle pin is what the voltage is sent through when magnet is lifted right? Or is that wrong?

 

[happyrat1]

USB 2.0 is unable to provide more than 500 mA of current at 5 VDC.

USB 3.0 is capable of supplying 900 mA at 5 VDC.

If your interface and USB port are both 2.0 then you are starving the ancient CMOS circuit in the accordion of current. The display in your pictures appear to be LED and I can tell you those are power hungry.

USB 3.0 WITH a USB 3.0 MIDI Interface MIGHT be able to supply it properly.

If not then see my suggestion about wiring in a 5 VDC 1 Amp adapter directly into the interface cutting the supply line from the computer or inserting some diodes to avoid reverse current flow.

Honestly I have my doubts about what you were told about the unit getting it's supply directly from MIDI. Have you actually seen one working that way?

Gary