Need help in trouble-shooting a midi issue.

Dears, midi input 1&2 are friggin' faulty on my 2.5K..

Output is just fine, but I can't get no satisfaction from the inputs. Monitor in Midi Menu stay silent no matter which bomb you throw at it. It's no for the notes and no for the CCs if you see what I mean.

NOW, what I've already gone thru is:

-JJOS reinstall with the latest updates (a couple times, since I both tested it under OS2XL and OS3 - full pay-version)

-MIDI ASSY PCB replacement (and it's a BIG PROP to RenatoRizoli for his help sourcing the part)

I start thinking the actual photcoupler (Avago HCPL-0701) on the main PCB (WHERE YOU ARE?!?) may be faulty... or the connector maybe?

What do you suggest?

Tested with multiple different input devices, or at least one known working input device tested with some other equipment?

SimonInAustralia wrote:Tested with multiple different input devices, or at least one known working input device tested with some other equipment?

Yes, external audio/midi interface and Midi Keyboard. No joy in both cases.

Midi keyboard works just fine with my external audio/midi card, both thru midicable than usb.

Midi out tested both with external audio/midi box, SP303 and 404. It works a threat.

Doesn't sound good.

Just wanted to make sure that if using a MIDI keyboard, which also has USB, that it is actually sending out MIDI from the keyboard to the MIDI ports, as some need to be powered from an external power supply, rather than USB, as when powered by USB, some don't send MIDI out of the MIDI ports.

I obviously powered the kb thru adapter and not usb to perform the tests.

Funkydrops wrote:I obviously powered the kb thru adapter and not usb to perform the tests.

Yes, it might be obvious, but you have to ask the obvious just to make sure.


The schematics show a separate photo coupler (PH1 and PH2) for each of the MIDI inputs, so not a single component to fail, and separate lines from the photo couplers into the CPU.

Unless something faulty was plugged into both inputs at some stage, and fried them both.

Maybe check for power into the photo couplers, and trace the connections out from the photo couplers to the MIDI board and ports, and the other way from the photo couplers into the CPU?

SimonInAustralia wrote:

Funkydrops wrote:I obviously powered the kb thru adapter and not usb to perform the tests.

Yes, it might be obvious, but you have to ask the obvious just to make sure.


The schematics show a separate photo coupler (PH1 and PH2) for each of the MIDI inputs, so not a single component to fail, and separate lines from the photo couplers into the CPU.

Unless something faulty was plugged into both inputs at some stage, and fried them both.

Maybe check for power into the photo couplers, and trace the connections out from the photo couplers to the MIDI board and ports, and the other way from the photo couplers into the CPU?

Looking at the schematics I was understanding that PH1 was serving input, while PH2 dealt with midi out ports...

To me, it looks like each MIDI input goes through a separate photo coupler.

PH1 takes it's input from MDI0P and MDI0S, PH2 takes it's input from MDI1P and MDI1S.

PH1 outputs a signal on the MDRX0 line into the CPU, PH2 outputs a signal on the MDRX1 line into the CPU.

The MIDI outputs go through the MDTXB0/MDTXB1/MDTXB2/MDTXB3 lines, which do not go through the 2 photo couplers.

Have a look at the schematic diagram for the MIDI PCB, check which lines on the connector are connected to the 6 MIDI ports, and reference those lines back to the CPU schematic diagram, you should see that the outputs do not go through the 2 photo couplers, only the inputs do.

Solved. I repeated the tests and managed to find what I was overlooking. Keyboard midi out port is faulty. I set up reaper to receive from usb midi and spit back via the midi interface to the mpc and kaboom!

Thanks, the first time I ran the crosstest I forgot to unplug the usb shit, so that my vst was getting the notes (doh) right... just not from the port I was testin' ...

I reran the full tests ONLY because of your advise. Lacking focus, I guess...

Funkydrops wrote:Thanks, the first time I ran the crosstest I forgot to unplug the usb shit, so that my vst was getting the notes (doh) right... just not from the port I was testin' ...

It's good that you worked out that it wasn't the MPC MIDI ports.

Some MIDI keyboards, when a USB cable is plugged into them (from a computer, or USB power supply), use their external MIDI ports as a computer USB-MIDI interface only, and do not output MIDI directly from the keyboard to the external MIDI ports, the MIDI output from the keyboard only goes into the computer over the internal USB-MIDI interface.

They need to have the USB cable disconnected from the computer (or USB power supply), and to be powered by an external power supply, to operate 'normally' as a non-USB MIDI controller in regards to their external MIDI ports. The Akai MPK MIDI controller keyboards, for example, operate like this.

Alternatively, if connected to a computer with a USB cable, the MIDI that is going from the keyboard into the computer over the internal USB-MIDI interface, has to be routed back out, from the computer, to the keyboard MIDI ports, which are operating as an external USB-MIDI interface for the computer.