MPC2000XL MIDI crash

I bought an MPC2000XL about a year ago, and to my frustration, recently discovered the MIDI OUT does not work. It crashes anytime I connect an external device to MIDI OUT A or B, and try to send notes. I'm wondering if anyone else has experienced this issue, and how they resolved the problem.

* The OS crashes a few seconds after sending notes through either of the two MIDI OUT channels. No error message, but the screen locks up, no buttons respond, and the MPC needs to be rebooted.
* If no device is connected to the MIDI OUT and notes are sent, there is no crash.
* If a device is connected but no midi notes are being sent, there is no crash.
* Tested two different external synths and both trigger a crash, so its unrelated to any specific device.
* Receiving MIDI IN works fine.
* Removing the extra memory and zip drive (the only add ons), did not fix the problem.

Have not heard of that.

Is there nothing connected to the MPC MIDI ins when you are trying it?

Yes, there is nothing connected to the MIDI INs, and I am playing notes from the drum pads. The external synth will play a few notes (often with glitches, like stuck notes and notes I didn't actually play), then the MPC crashes after a few seconds.

I tried reflashing the OS, but it didn't help.

neon128 wrote:I tried reflashing the OS, but it didn't help.

With a fresh download?

It might be a motherboard brain.

Its a bit late, but why did it take you a whole year to test the midi outputs?

I was able to fix it by replacing a 50 cent chip that turned out to be the culprit. If your MPC has the same problem and you're comfortable soldering surface mount components, this could save you the expense of a new motherboard.

The crash only happens when sending MIDI data while the port is under load, so I figured the gates on IC78 are faulty and can no longer sink enough current to drive the MIDI current loop. The other gates on this chip control an interrupt line from the UART to the microcontroller, so its plausible MIDI OUT load is pulling these gates high and strobing the OS's interrupt handler.

The original chip is a Hitachi 74HC32 which is no longer available, but any 74HC32 in 14-SO "wide" format should work. The one I used was a Texas Instruments SN74HC32NSR.