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Author Topic: MIDI Busted on MP-1  (Read 266 times)

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mrguitar

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MIDI Busted on MP-1
« on: Time Format »

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,
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van Sinn

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Re: MIDI Busted on MP-1
« Reply #1 on: Time Format »

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..
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mrguitar

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Re: MIDI Busted on MP-1
« Reply #2 on: Time Format »

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,
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MarshallJMP

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Re: MIDI Busted on MP-1
« Reply #3 on: Time Format »

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!!
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mrguitar

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Re: MIDI Busted on MP-1
« Reply #4 on: Time Format »

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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MarshallJMP

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Re: MIDI Busted on MP-1
« Reply #5 on: Time Format »

Ok next try to remove the opto, it's a 6 pin dil ic in a socket on the midi board, should be a PC900 or an H11L1 and try it without this opto.
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mrguitar

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Re: MIDI Busted on MP-1
« Reply #6 on: Time Format »

Great thanks. I'm out of town this week, but I'll report back this weekend.
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mrguitar

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Re: MIDI Busted on MP-1
« Reply #7 on: Time Format »

This unit has the PC900 Sharp IC in it, and unfortunately I get the exact same behavior w/ the chip removed. .....now I'm realizing that I forgot to check which direction the IC was installed (noob mistake - should have taken a picture). I *think* pin 1 was closest to the MIDI input on the unit as apposed to facing the UART. Can you confirm if that is correct?

Hopefully this rules out the IC.

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van Sinn

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Re: MIDI Busted on MP-1
« Reply #8 on: Time Format »

The chip itself has pin 1 clearly marked, and the socket always have some notch or whatever at the end where pin 1 is located.
Don't know if that chip will be damaged if installed the wrong way - it's all merely about ground and 5 volt signals so it may've survived; just pay notice if reinstalling it correctly doesn't carry expected results..
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MarshallJMP

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Re: MIDI Busted on MP-1
« Reply #9 on: Time Format »

This unit has the PC900 Sharp IC in it, and unfortunately I get the exact same behavior w/ the chip removed. .....now I'm realizing that I forgot to check which direction the IC was installed (noob mistake - should have taken a picture). I *think* pin 1 was closest to the MIDI input on the unit as apposed to facing the UART. Can you confirm if that is correct?

Hopefully this rules out the IC.

Here's a pic.

You can try to replace the uart but I'm not 100% sure this will solve the problem, could also be one of the supporting chips. You can find those uart chips on ebay.
Look for a COM8052, TR1863 or a COM8017, or the more modern HD3-6402R-9 will also work.
« Last Edit: Time Format by MarshallJMP »
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mrguitar

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Re: MIDI Busted on MP-1
« Reply #10 on: Time Format »

Thanks van Sinn & MarshallJMP.

I went ahead and ordered a COM8017 from ebay and I'll give that a shot as the next step. $10 to rule something out isn't too bad. If one of the surrounding DM74LS04N (or 74LS541N) ICs is the problem I'll probably take it to someone who can test to find the faulty one. I'll probably do more harm than good if I start trying to swap those. I'll also throw in a new opto as well since they're cheap and can be dropped into the socket. It will take a while to get the parts but I'll post an update w/ the progress.

thanks again for all the help!

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MarshallJMP

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Re: MIDI Busted on MP-1
« Reply #11 on: Time Format »

Ok keep us updated!
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mrguitar

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Re: MIDI Busted on MP-1
« Reply #12 on: Time Format »

I just got the new COM8017. Popped it in; and it works like a champ!!

I no longer get a constant stream of garbage when listening to the midi out port. The changes are instant and work perfectly from the Kemper and Kemper Remote.

......still tempted to buy this: https://www.ebay.com/itm/ADA-MPC-MIDI-PROGRAM-CHANGER-Foot-Switch-Controller-w-7-pin-Phantom-Power/302910036926?hash=item4686d85bbe:g:37wAAOSwPfBbt7ka:rk:1:pf:0
That was the foot controller I had back in the 90s. I thought they did a phenomenal job on that one.

Thanks again for all the help!
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rnolan

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Re: MIDI Busted on MP-1
« Reply #13 on: Time Format »

 :whoohoo!: :thumb-up:
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MarshallJMP

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Re: MIDI Busted on MP-1
« Reply #14 on: Today at 01:15 AM »

Thanks for letting us know  :thumb-up:
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