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  #1  
Old 01-31-2014, 03:52 AM
jordan jordan is offline
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Default Troubleshooting MPA connection with computer

I have purchased and assembled the MPA 100k. My SysEx send is not registering activity on the LED. This is the code:

F0 00 01 5D 01
05 02 01
05 02 02
05 02 03
05 02 04
05
00 3C
00 3D
00 3F
00 40
00 41
00 42
00 43
00 00 00 00 00 00 00 00
00 00 00 00
F7

I suspect that I have a broken signal diode. My voltmeter is reading ~ 600 and ~ 700 units in respective polarity orientations of the Diode setting.

When plugged in, the activity LED does light up and turns off as it should.

I have checked voltage across all Logic terminals with midi notes triggered from C4-G4 and there is none.

I am aiming to trigger a Mattel Synsonics Drum Machine with the logic outputs 0-3 (4 sounds) and use the potentiometers to filter the sounds via a few mods that are documented on burnkit2600.com .

Does this activity of the LED on startup, and lack of activity otherwise make sense if the diode is leaking current across the bias?
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  #2  
Old 01-31-2014, 04:08 AM
jordan jordan is offline
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I switched the Diode for an 1N914 (which is equivalent as far as I can tell: http://en.wikipedia.org/wiki/1N4148), but the problem persists.

I test the midi thru using SQWRL and it is testing positive, on all channels.

I have checked the potentiometer resistances and they all correspond to ~ 46k per side of each wiper, which leads me to believe that the unit is in its default configuration.
Testing the default configuration output however doesn't work out. Sending note triggers to middle C (on the correct corresponding channel to the switch) does not result in a 5V output on Logic 0.

The Power Out is consistent with 5V out put.

It would seem that everything is working EXCEPT processing midi/SysEX information.
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  #3  
Old 01-31-2014, 12:55 PM
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Synthetech Synthetech is offline
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Hi, maybe I can suggest a few things until John can respond...

I guess the 1st thing to ask is, what MIDI interface are you using??

Also, if you can find a setting in the MIDI utility program to lower the buffer size down to say.. 256k and even as low as 128k..
I do know that some MIDI devices cannot handle too much data too fast..

HTC's
-Blaine
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  #4  
Old 01-31-2014, 04:17 PM
jordan jordan is offline
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Thanks for the tip. I am using a m-audio profire 610. I will try this out now.
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  #5  
Old 01-31-2014, 04:52 PM
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I lowered the buffer size (Transmit Speed) in SysEX Librarian to 128 samples and the message did not register in the MPA's LED. I tested the outputs with a midi trigger from ableton at 128 sample buffer size and there is no voltage output.

puzzling, but thanks for the advice regarding buffer size, I had not considered that at all.
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  #6  
Old 01-31-2014, 07:23 PM
jordan jordan is offline
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I also just re soldered any connections that seemed to have imperfections, or looked like cold solders, but the problem persists.
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  #7  
Old 01-31-2014, 08:00 PM
jordan jordan is offline
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Could anyone possibly provide some rudimentary instructions for verifying voltages across the pins of the IC's to check if they is functioning as they should?
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  #8  
Old 02-01-2014, 07:32 AM
jordan jordan is offline
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IC1 voltage across Vpp to Vss and Vss to Vdd read 5V. I suppose this implies that the chip is functioning

http://ww1.microchip.com/downloads/e...Doc/41250F.pdf - specs on the chip
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  #9  
Old 02-01-2014, 02:07 PM
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It only means it is getting voltage.. not an indication that it is functioning.


have you checked the 7414 Hex Inverter?

Pin 14=5v
P7=Gnd
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  #10  
Old 02-01-2014, 02:32 PM
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I'd also check the Optoisolator (OI).. the small IC chip next to your MIDI jacks...

P8= 5v
P5= Gnd


if this part isnt working, you will not get any MIDI in data.


I would also check with a continuity test for each leg of that OI chip.. check one end on each of the legs on the IC itself and see if it passes thru the socket it's in and on to the solder joints on the back side.. this will determine each leg is seated correctly with no bent legs, damaged socket, etc.

I have a feeling the problem is centered around the OI since you get no midi in... and because the LED activity light wont come on when you try to push data in thru the MIDI IN port (the PIC lights it up though).

That 7414 Hex inverter looks like it is only used to pass on the MIDI THRU data.. I think. It seems there is only one or two inverters actually used on it and the extra ones are not used at all... so I'd forget about looking at it anymore.

I have a couple of the MPA's here to refer to.. I have not built them yet, but am looking at mine to try to help you fix yours.

HTH's
~Blaine

Last edited by Synthetech; 02-01-2014 at 02:53 PM.
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  #11  
Old 02-01-2014, 03:25 PM
jordan jordan is offline
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Ok : I checked those pins, and they seem fine.

Here's the voltages of all the IC1 pins:

1 - 5V
2 - 5V
3 - Gnd
4 - 5V
5 - 5V
6 - Gnd
7 - Gnd
8 - Gnd
9 - Gnd
10 - Gnd
11 - Gnd
12 - Gnd
13 - Gnd
14 - 5V

15 - 5V
16 - 5V
17 - 0.35V
18 - 5V
19 - Gnd
20 - 5V
21 - 5V
22 - 5V
23 - 5V
24 - 5V
25 - Gnd
26 - Gnd
27 - Gnd
28 - Gnd

The Potentiometer IC's are reading identical values.

IC2 reads all ground except pins 6 and 8 @ 5V

IC4 reads as follows:

1 - 5V
2 - Gnd
3 - Gnd
4 - 5V
5 - Gnd
6 - 5V
7 - Gnd

8 - 5V
9 - Gnd
10 - 5V
11 - Gnd
12 - 5V
13 - Gnd
14 - 5V
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  #12  
Old 02-01-2014, 03:47 PM
jordan jordan is offline
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Thanks so much for the help Blaine ! I am checking continuity right now
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  #13  
Old 02-01-2014, 03:48 PM
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Pin 18 on IC1.. that appears to be MIDI data in from the OI.


It's probably set to default as a pullup resistor (R2) and will read 5v while idle.

What I'd try to do is monitor it while you send it a bunch of 1's or 0's at it. See if it changes to Gnd.

Try sending hundreds of FF's first and monitor that pin. If it changes value for a period while it is streaming in the data from your interface, then it means we are getting data thru to the PIC's input. (also try sending it 00's to see if that does anything).

send it this while monitoring...

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF



or these

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

one of those groups of bytes should provoke a response at P18.
P6 on IC2 should also be the same since IC1P18 and IC2P6 are directly tied to each other.


HTH's

Last edited by Synthetech; 02-01-2014 at 03:54 PM.
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  #14  
Old 02-01-2014, 05:04 PM
jordan jordan is offline
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I pulled this up: http://www.vishay.com/docs/83604/6n135.pdf and the guts of the OI are working perfectly (both diodes check out and the voltages through the transistor are as they should be).

Continuity does not seem to be the issue either
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  #15  
Old 02-01-2014, 05:06 PM
jordan jordan is offline
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ok great, attempting to test the midi in now
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  #16  
Old 02-01-2014, 05:11 PM
jordan jordan is offline
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Do I need to send the FF FF FF etc or 00 00 00 00 etc. after the device header, F0 00 01 5D 01 , and before the Footer, F7 ?

like:

F0 00 01 5D 01

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

F7
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  #17  
Old 02-01-2014, 05:31 PM
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just the FF's and then try 00's

no header or footer, we are just sending raw data to see what the OI's output does at the IC1P18 input.
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  #18  
Old 02-01-2014, 07:34 PM
jordan jordan is offline
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Hey, unfortunately i am now unable get the loop back test to pass. I am wondering now if there was something i shorted or altered while probing around the board.

also, SysEX Librarian won't accept a .syx file containing strings of 00s or FFs. It claims there is no sysex content within it. Do you recommend another application to send this information ?

This project is unfortunately time sensitive. I may order a new board (they're on sale i believe ! ) and use this one for future experimentation.
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  #19  
Old 02-02-2014, 02:35 PM
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are you using a mac or PC? I assume mac since you mentioned sysex librarian.


I have a PC and only use sendSX. It allows me to send arbitrary data without the F0/F7 header/footers.


When you mention a "loop back test" what are you specifically talking about? A command sent to the MPA and a response back at it's OUT port (not the THRU port..)???
If your midi utility app wont send a msg without a F0/F7, then put them in and send out the FF's and or 00's.

I doubt you have hurt it anymore than it might already be if all you did was probe with a DMM.. sorry for your troubles.
Do you happen to have a scope to use as well as a DMM/voltmeter?

You might try to contact John at
info@highlyliquid.com
for direct support

it may take a few days to get a response

-Blaine

Last edited by Synthetech; 02-02-2014 at 03:17 PM.
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