Let's Get Technical > All PREAMP Tech Tips & Support
MIDI Busted on MP-1
mrguitar:
Alright, time for the next chapter of my MP1 adventure, I've discovered that the unit is unresponsive to midi program changes.
I was originally trying to send program changes via my kemper. After that didn't work I was able to use: https://github.com/gbevin/SendMIDI & https://github.com/gbevin/ReceiveMIDI and verify my cables and kemper side. I can see that the midi thru is indeed working on the MP-1; meaning I'll see the program change come back through. but the unit is not responsive to program changes. I've tried every combination of channels & omni that I can think of too.
I did find this tips sheet here: http://www.marshalljmpmodshop.net/ADA-MP1-troubleshooting-tips-1992.pdf
and I see that I can purchase an 1807 chip from marshalljmp's shop (which I probably will). ....but I want to do my due diligence to make sure this is *the problem* and not a symptom of something else. While tweaking the midi channels, I was able to recreate the last problem I ran into here: http://adadepot.com/index.php?topic=2253.0 I basically locked up the unit and none of the buttons were responsive. This makes me wondering if the problem is beyond the uart chip.
I'm curious if the condenses here is I should just swap the chip or if there's more that should be ruled out. Unfortunately I don't own a scope, just a multi-meter. I'm good w/ an soldering iron, but not at tracing circuits. I fear this diagnostic may be beyond my skill level. Anyway, thanks in advance for any input on this.
Cheers,
vansinn:
MIDI-through is working, which is simple to understand, because MIDI-through is merely passing the input almost directly to out/through via a transistor (IIRC).
If you connect your MP-1 MIDI-out/through to another device (like your masonic Kemper) and manually change presets on the MP-1, do the other device change presets accordingly?
If so, the UART likely isn't broke - likely, because, of course it could be defect on one channel..
mrguitar:
Wow, so the midi out is just pushing crazy noise constantly. (for comparison, none of this noise is preset when capturing from the kemper)
Here's an example of a short capture & changing from path 14 to 15 using the up arrow on the MP-1:
reset
reset
reset
reset
reset
active-sensing
reset
reset
active-sensing
channel 16 control-change 126 0
reset
reset
reset
active-sensing
reset
reset
Here's a longer capture moving from 1-14. (I trimmed out hundreds of lines here and apologies for the long post. I mostly cropped a bunch of "resets" and :"active-sensing" for readability.)
$ ./receivemidi dev E-MU XMidi1X1 MIDI 1
reset
active-sensing
reset
reset
active-sensing
active-sensing
active-sensing
reset
reset
tune-request
active-sensing
reset
reset
start
channel 8 pitch-bend 16382
reset
reset
reset
active-sensing
reset
reset
active-sensing
reset
reset
reset
channel 15 program-change 127
reset
reset
active-sensing
reset
reset
channel 8 pitch-bend 16383
reset
reset
reset
channel 15 program-change 127
reset
reset
channel 8 pitch-bend 15743
reset
active-sensing
reset
reset
reset
reset
channel 16 pitch-bend 16383
reset
active-sensing
reset
reset
channel 16 channel-pressure 127
reset
channel 16 channel-pressure 127
reset
reset
reset
reset
channel 16 channel-pressure 127
reset
reset
reset
reset
channel 16 pitch-bend 12286
reset
channel 15 program-change 127
channel 15 program-change 127
reset
continue
reset
reset
reset
reset
channel 16 pitch-bend 16379
reset
active-sensing
reset
continue
channel 8 pitch-bend 0
channel 8 pitch-bend 0
channel 8 pitch-bend 0
channel 8 pitch-bend 0
channel 8 pitch-bend 0
stop
channel 8 pitch-bend 0
reset
stop
reset
reset
reset
reset
active-sensing
reset
reset
channel 16 pitch-bend 127
channel 16 pitch-bend 0
channel 16 pitch-bend 0
reset
channel 16 pitch-bend 16000
reset
continue
reset
active-sensing
reset
active-sensing
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
active-sensing
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
channel 16 pitch-bend 0
channel 16 pitch-bend 4
channel 16 pitch-bend 0
channel 16 pitch-bend 0
midi-clock
reset
reset
reset
reset
reset
reset
reset
reset
reset
active-sensing
reset
active-sensing
reset
channel 15 channel-pressure 0
channel 15 channel-pressure 0
channel 1 program-change 0
channel 1 program-change 0
channel 1 program-change 0
channel 1 pitch-bend 0
channel 1 pitch-bend 0
channel 1 pitch-bend 0
continue
reset
reset
reset
reset
reset
reset
active-sensing
channel 16 pitch-bend 0
channel 16 pitch-bend 0
channel 16 pitch-bend 0
channel 16 pitch-bend 0
channel 16 pitch-bend 0
channel 16 pitch-bend 0
channel 16 pitch-bend 0
channel 16 pitch-bend 0
reset
reset
active-sensing
reset
reset
reset
channel 16 pitch-bend 0
channel 1 note-off C-2 0
channel 1 note-off C-2 0
channel 1 note-off C-2 0
channel 1 note-off C-2 0
channel 1 note-off C-2 0
channel 1 note-off C-2 0
channel 1 note-off C-2 0
continue
reset
reset
reset
active-sensing
reset
reset
channel 16 pitch-bend 0
reset
reset
channel 11 pitch-bend 13247
reset
reset
active-sensing
reset
channel 16 pitch-bend 0
channel 16 pitch-bend 0
channel 16 pitch-bend 0
reset
reset
reset
reset
channel 8 pitch-bend 0
channel 8 pitch-bend 0
reset
reset
start
reset
reset
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 4159
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
channel 16 pitch-bend 63
I think it's reasonable to think the UART is bad. I'd be interested if you guys think that's the case, and if there are other parts that can cause these to fail that should also be replaced.
Cheers,
MarshallJMP:
I would try something very simple first and that is to unplug/replug the grey flat cable on the midi board and mainboard just to make sure there are no bad contacts there.
Make sure you plug it back in correctly!!
mrguitar:
Thanks for the idea. I just tried it and I'm seeing the same behavior after carefully re-seating the ribbon cable.
I'm actually curious if you plug the midi out to a PC on a working unit if it sends crazy streams like this. I would think it wouldn't, but I can't verify.
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