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SC-88 stopped working when attached to MPU-401

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First post, by shadmere

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Today I got an SC-88 and was super excited to hook it up. I connected it to the MPU-401 on my 486 and ran the install program for King's Quest 6 in DOS. I set it for General MIDI and . . . it sounded great!

I started Windows and installed the MPU-401 driver. Set up a new MIDI map where all the channels were sent to the MPU-401 port, saved it, and played a MIDI. It sounded wonderful!

KQ6 for Windows was already installed, so I was thinking that it would "just work," since it was already set for MIDI output. I thought that since I had set Windows MIDI map to MPU-401, it would just go out through those channels. Unfortunately it did not work.

I tried changing MIDI maps a few times just in case, and restarted Windows, but nothing worked. Finally I went to play a MIDI file again and . . . it didn't work. The LCD on the SC-88 didn't register that it was getting input at all.

I quit to DOS and ran KQ6 there. Same thing; no music, no activity on the LCD.

I unhooked the SC-88 and hooked up my MT-32. Music!

I pressed the volume knob on the SC-88 and heard a tone. I hooked the SC-88 up to my modern PC with a USB-to-MIDI cable and ran a game in DOSBOX. It worked.

I hooked the SC-88 back to the MPU-401 on the 486 and . . . it does not work.

Seems like I can guarantee that the MPU-401 is working. And the SC-88 seems to be working too. But not together.

I am confused. I opened up the box to look at it and am a bit over my head here, but shouldn't any issues that kept it from working with the MPU-401 also keep it from working with my modern computer? (While in there, I removed the battery. I've read on here in a couple places that the battery doesn't matter for gaming, and I'd rather not risk it exploding because I forgot to change it.)

TL;DR:

SC-88 hooked up to MPU-401 does not work. No activity on LCD whatsoever.

MT-32 hooked up to MPU-401 does work.

SC-88 hooked up to modern PC with MIDI cable does work.

SC-88 does give a test tone when volume knob is pressed.

I'm not sure what troubleshooting steps to try next. I would love some advice. Thank you.

Reply 1 of 7, by darry

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Are you using an actual Roland MPU-401 or sound card with an MPU-401 compatible MIDI port that connects to the module with a joystick port to MIDI adapter ?

If using a joystick MIDI adapter cable, I have a hunch that it is an out of spec cheap one that does not have an opto-isolator and that there is causing an issue with the SC-88 (possible ground loop).

Maybe I'm off-base here, but it's a hunch

EDIT: The MT-32 may be more tolerant .

Reply 2 of 7, by shadmere

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Actual MPU-401.

And the SC-88 did work at first. It worked in DOS, and it worked in Win 3.1 after I installed the driver. Well, it worked for playing MIDIs at least. I never got it to work in KQ6 in Windows, and after trying to, it stopped working in both Windows and DOS.

Reply 3 of 7, by darry

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shadmere wrote on 2020-09-05, 23:19:

Actual MPU-401.

And the SC-88 did work at first. It worked in DOS, and it worked in Win 3.1 after I installed the driver. Well, it worked for playing MIDIs at least. I never got it to work in KQ6 in Windows, and after trying to, it stopped working in both Windows and DOS.

In that case, it is very strange indeed .

I imagine the switch is set to MIDI on the SC-88 . Also, have you tried both MIDI inputs ?

Reply 5 of 7, by darry

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shadmere wrote on 2020-09-05, 23:51:

::checks::

Yes, it's set to MIDI.

And yeah, neither work (from the MPU-401 at least).

Hmm, how about connecting the MT-32 to the MPU-401 and cascading the SC-88 off the MT-32's MIDI thru port ?

Reply 6 of 7, by shadmere

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Okay, well. That didn't work, but now I can't get the MT-32 to work either. When turned on, it says "**Roland MT-32**" on the LCD but never changes from that. The "MIDI message" light stays on at all times, even when it's not connected to anything.

That doesn't seem related to the SC-88 problem that I can see, but it's certainly some kind of problem.

Reply 7 of 7, by shadmere

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Update:

This morning, at least, the MT-32 is functioning again. It flashes "**Roland MT-32** on startup, like usual, then goes to the view where you see channels 1-6.

I don't know why last night it would only display that startup message, then freeze. That worries me about the internals, I guess? Should it? 🤣.

Now back to figuring this SC-88 thing out.

Edit: It all works now. I don't know why, but everything has been working normally for the past hour or so. Huh.

(Not a real edit; I came back to edit the comment and saw that I got an "Invalid form submitted" error for some reason. Which makes the edit irrelevant.)

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