HELP I got an old Accordion with Midi interface

[happyrat1]

BTW, a silicon diode induces a voltage drop of 0.7 VDC when forward biased.

Gary

 

[happyrat1]

And the magnetic devices are Hall Effect Sensors. Check the specs for the part numbers. They also incur a forward voltage drop when activated.

Gary

 

[blaze_01]

I actually thought about the power through usb.
So i used an usb adapter into the wall at 2.4a when measuring.

Well there is nowhere to find an actual input for a powersupply. I got mail adress now to those who made the old system. If they even use the mail anymore. Maybe i can get some info.
But i guess they just gonna try to sell me the 1800eur sound module xD

A guy using these old midis long ago said they were powered with 5v through the cable from an external box.
This system is so old now days, if i ever gonna see one powered up, it must be mine

So you suggest i power it from inside? Lets say i wire up som batteries to 5v and try to connect them to yellow and brown wire maybe? Just to see if the display lights?

 

[happyrat1]

And also FYI, the forward drop on a germanium diode is only 0.3 VDC.

Spec your components accordingly.

Gary

 

[happyrat1]

I'd suggest cutting the power supply or blocking it with a diode leading from the interface and wiring a wall wart into the beast directly.

Yeah, that's how I'd do it.

Gary

 

[happyrat1]

Drill a quarter inch hole in it and use a 3.5 mm phone jack to plug the supply into the accordion if it works.

Gary

 

[happyrat1]

WARNING!!!!! Make certain you are using a REGULATED POWER SUPPLY or batteries to power it.

Any unregulated supply could easily blow the circuit.

Operating voltage of 5 VDC indicates that it's CMOS or some vairant of MOS family of circuitry.

Gary

 

[happyrat1]

Is the part number 54 or 74 inside the unit?

54 is CMOS family.

74 is TTL.


EDIT >>> Actually LS is Low Power Shottky Transistor Family

EDIT >>> What's the exact chip number on the chip?


Gary

 

[happyrat1]

It occurs to me that you could simply wire up an adapter cable that accomplishes what the original power supply black box did.

here's a rough schematic.

Gary

 

[happyrat1]

Use a 220 Ohm 1/2 Watt Resistor for the Resistor

Gary

 

[blaze_01]

Damn this got back to the electronics i did at school very long ago, i went two years but i've forgotten everything haha.
I do kinda understand the image though and see what you did there. But i do not have any of the items listed.

I however stumbled across something.

I had a look at the wiring on the display.

The red. White. Blue. Brown. Grey. Cable goes up to the display. The same cables also goes down to the board inside.

However the yellow cable goes straight down to the board.

The yellow wire would be pin5
And the red pin4.

If the display needed 5v to power up, wouldnt i then run 5v through both pins?
Sorry i got lost in electronics.

But how its connected now, using usb, the usb give 5v at the yellow cable. And 1.6v at the red (pin4) which goes to the display.

I dont know how lost i am now but i started woundering if the pins on the female here could have been reversed?

The wires from display also goes down to the board and through the midi out.

I wounder if its reversed, if its really the yellow cable thats supposed to power the thing? Cause the red cable is the only cable going to the display from the actual midi input, but the usb wiring (as intended on other instruments) doesnt seem to carry more than 1.5v.

I dont know if the pinout i found on google is right but it seems 5 is data. 2 is shield and 4 is voltage.
If thats the case then its reversed.

I got some pictures.

 

[happyrat1]

Yeah, the Male and Female plugs are mirror images.

Double check with google that you get the right pinouts else it all goes FLOOOOOEYYYYYYYY!!!!! ~~~

Gary

 

[blaze_01]

Btw here is the explanation i got:

The box supplies the regulated 5 volts thru the
"firing cable" to the accordion. It also takes the midi signal from the accordion via the same cable and is available at the box via a dedicated connector to connect to a "sound generator".

 

[happyrat1]

It's basically a T-Shaped adapter box or cable, your choice.

All you need is a decent 5 VDC adapter, some shielded multistrand cable, a 5 Pin DIN female and male connectors, a 220 Ohm 1/2 Watt Metal Film Resistor, some heatshrink tubing or electrical tape, solder and an iron and you should be good to go.

All of these items are readily available on Amazon or Ebay from China if you don't mind waiting 6 weeks for them to arrive.

Test it with 3 or four AA Batteries first to confirm, and it should work.

Attach it to the MIDI OUT of the adapter and the MIDI IN of the accordion and you should see life in the old girl.

Gary

 

[blaze_01]

Thankyou!
Now this is interesting. I thought it was worse.
So i got most of the items then.
Maybe i could disassemble something i got lying around for that resistor there.



Is the resistor a must or do you think the system can survive a few houndred extra mv?

I just gotta ask, how is midi supposedly working (in my situation) ?

Which of the pins are actually transmitting power?
4 or 5 or both?

Is input information is sent through same wire as the 5v.?

One pin goes straight to the circuit board? Where the other pin goes to the display and then to the board.
Just for the sake of testing with batteries first which i am tempted to do.

I wouldnt want to burn this thing up.
I actually found the microcontroller for sale at ebay for 37eur, so i realised it wasnt cheap haha

 

[happyrat1]

Basically Pin 5 is data, Pin 2 is Ground and Pin 4 is VCC+

Gary

 

[happyrat1]

I would use the resistor. It's a current limiter in case the system shorts out and fries the source. It's definitely part of the MIDI spec.

Gary

 

[blaze_01]

Ok so i figured then.
In my case the red wire is data and the yellow wire is 5v.

The red wire goes to the display. I still cant understand how the display is powered.

The 5vpin yellow goes to the microcomputer first then.

Alright, so for testing this i would connect power at yellow and brown.


But how come this didnt work with my usb in the first place then? Too low current?

 

[happyrat1]

Double check your pinouts.

Gary

 

[blaze_01]

So that makes pin4 yellow then haha.

Here is the current draw i got. Still not powered on though