No sound output from LAPC-I

[Death Adder]

Hello, folks.

I recently bought a LAPC-I because, quite frankly, I'm a lazy man. To me, an ISA card is much less hassle than an MT-32 box + all the connectors. So I unhooked my MT-32 and put it away, and plugged the LAPC-I into the same ISA slot where the MT-32 interface card had previously been. All right! Ready to go! Not quite.

Dune II, a game which always worked flawlessly with my MT-32, detected the LAPC-I just fine, initialized it, and started up all right - but I'm not getting any sound output! Same result with several other games: they can initialize the LAPC-I without trouble, and they seem to be sending data to it - but I'm not hearing a damned thing.

I'm pretty sure the problem just has something to do with me being stupid, which is embarrassing, but I'd really like to get the issue resolved so I can enjoy my lazy new purchase. I've tried to connect speakers to the LAPC-I via its headphone jack and via the red and white jacks, but all I get is jacked.

Help definitely appreciated, as I don't feel like digging out my entire MT-32 setup and hooking it all in again... thanks in advance.

[Caliburn]

Well, I'm an MT-32 user and have never had an LAPC-I, so you might get better help from someone else, but what operating system are you using?  Does it employ any software mixer that might have placed a mute on the LAPC-I?

-Luke

[Death Adder]

I'm using a 486 with DOS 6.22 and absolutely none of that Windows garbage.

There's nothing in place that should be doing anything to stop the LAPC-I from working, which is why I'm assuming the problem is just the result of me making a mistake somewhere.

[Great Hierophant]

The only thing I can suggest is to make sure your LAPC is set to the right I/O setting and nothing else is conflicting.  Games use 330 by default, the LAPC can use 330, 332, 334, 336, 338.  Try other games too (make sure Dune 2 isn't muted.)

[Caliburn]

Well, even in DOS there might very well be a software mixer involved if you send the LAPC-I's output to a soundcard's Line-In before it goes to speakers.  I recall the SB16 as having a Creative mixer or something like that.

The only other thing that comes to mind is that I wonder if an interrupt conflict could make it seem like you were receiving data successfully while nevertheless preventing output.  I assume you checked all the other IRQs that the computer was already using and then set the jumpers on the LAPC-I accordingly?

-Luke

[Death Adder]

I'm assuming there's a conflict then, because I've tried hooking the LAPC-I to my line-in and just straight to a speaker. The MT-32 worked fine, but the LAPC-I is silent. I was using the MT-32 with the same exact computer, with the same exact hardware/software settings. The only thing I've changed is to remove the MT-32 interface card and put the LAPC-I in its place.

My BIOS only has parallel port interrupt at 378h IRQ7 and serial at 3F8h, but these should both be irrelevant.

I don't have any settings or jumpers set for the LAPC-I. This is accomplished how?

[glendower]

http://www.synthman.com/roland/support/supplementalnotes/SUPNOTES/MPUCARDS.html

Here's a site that shows you what the different jumper settings are for the LAPC-I

The jumpers themselves are toward the middle of the card, but more "front middle" I believe. Do you have a place for jumpers but no jumpers themselves?

[Death Adder]

Do you have a place for jumpers but no jumpers themselves?

I have jumpers for J07 and J08 only, the rest just have a place for jumpers. I've tried messing with the jumpers a bit, as described in the link you provided, but have had no luck yet. With different jumper settings, the games either lock up the system trying to initialize the LAPC-I, or I get the same result as before: no sound.

I've contacted the guy I bought it from, and despite him saying it was working, he now says this: "As I recall it was touchy in the sense it responded only to one MIDI channel and if it was right it seemed to be fine." - Which, of course, makes very little sense. D'oh!

Thanks for the help so far, guys. I'll keep plugging away...

[Cloudschatze]

I have an LAPC-I with a damaged MPU section. While this doesn't sound like the issue you are encountering, I wonder if you might humor me by trying the following:

Enter debug
You'll have a "-" prompt now.

Enter o 331 ac (Sends the AC command byte, "Version Request" to the MPU's data command port at address 331h.)

Enter i 330 (Checks the Data port at 330h. You should receive an "FE", which is an acknowlegement of the version request command that you sent.)

Enter i 330 again. (Checks the Data port again, but for the version byte. This time, you should see "15." In other words, version 1.5.)

Enter quit to exit the debugger.

[Death Adder]

This time, you should see "15." In other words, version 1.5.

Sure, it says 15.

[Cloudschatze]

This time, you should see "15." In other words, version 1.5.

Sure, it says 15.

Good. So, the MPU is probably OK. One less thing to wonder about.

Testing the LA section is not going to be easy (as in, I'm not sure how to go about it). There are two MIDI test points on the LAPC-I. You might try sending a data request to the LA synth, while probing the TxD "loop" with a multimeter (or an RCA cable hooked up to a speaker, as NewRisingSun pointed out). On the output side, probe a few of the DAC pins as well, to see if it is receiving data.

One other thing to consider - if the EPROM is socketed, you might try removing and re-seating it. Depending on the socket type, it can be beneficial to bend one the rows of pins (or both) out a bit, for better contact.

[Caliburn]

I have jumpers for J07 and J08 only, the rest just have a place for jumpers.

Sorry, let me make sure I understand this.  Since the J07 and J08 jumpers are the two that are used for setting the Port Address (presumably to 330, currently), and you say "the rest have just a place for jumpers," does that mean there is no jumper on any of the pins that are meant for setting the IRQ (in other words, locations J01-J06 have only pins and are empty)?

If so, can an LAPC-I user confirm how the device will behave under these circumstances?  Does it merely use the default IRQ of 2/9?  This is probably nothing and I don't want to distract from more fruitful lines of inquiry, but I thought I'd check.

-Luke

[Great Hierophant]

If so, can an LAPC-I user confirm how the device will behave under these circumstances?  Does it merely use the default IRQ of 2/9?  This is probably nothing and I don't want to distract from more fruitful lines of inquiry, but I thought I'd check.

In that case, the MPU-401 would not be able to use any IRQ at all, because the function of the jumper is to connect one of the IRQ lines on the ISA connector to the electronics on the card that use it.  Putting a jumper on one, preferably IRQ2/9, wouldn't hurt. 

An alternative method for testing the device is to use the whole computer as a midi device from another computer.  Before I discovered the joys of external modules, this was the method I principally used.  This requires the Roland MCB-1 breakout box, however. 

[Death Adder]

Since the J07 and J08 jumpers are the two that are used for setting the Port Address (presumably to 330, currently), and you say "the rest have just a place for jumpers," does that mean there is no jumper on any of the pins that are meant for setting the IRQ (in other words, locations J01-J06 have only pins and are empty)?

Here's what my board looks like:



The IC3 is also socketed, with a silver sticker over the chip reading "LAPC-I" followed by three rows of numbers:
First row (numbered 1-9): "1" is circled in red
Second row (numbered 0-9): "0" is circled in red
Third row (numbered 0-9): "0" is circled in red

[Great Hierophant]

I would bet you  that J01 is connected to the IRQ2/9 pin.  It should be easy to trace, find an ISA pinout to confirm it. 

[Death Adder]

An alternative method for testing the device is to use the whole computer as a midi device from another computer.  Before I discovered the joys of external modules, this was the method I principally used.  This requires the Roland MCB-1 breakout box, however.

I have the MCB-1 breakout box. Would you mind sharing instructions on how to use the whole computer as a MIDI device from another computer?

I would bet you that J01 is connected to the IRQ2/9 pin.

After carefully re-reading all of the info from the page glendower linked to, I'd tend to agree.

[Great Hierophant]

Excellent!  What you do is to turn your computer on with the LAPC to give it power.  Then connect the midi out of another (usually but not necessarily more advanced) computer to the MCB-1 midi in (making sure the MCB-1 is attached to the LAPC).  In this fashion your LAPC computer has become a midi module!  Make sure that the music you send to the LAPC does not contain custom patches, because the MPU-401 interface on the LAPC does not allow sysex transmission by default (there is a program available that can change this, but keep it simple for now.)

[Death Adder]

Thanks for the info. I've tried it and the result is the same as always: no sound. I wanted to make certain, so I swapped computers and tried again. No sound. I plopped the LAPC-I into a different computer and tried again: no sound. It would now truly appear that I am the owner of a non-working LAPC-I...

[glendower]

Can you go into your PC's BIOS and reserve IRQs? You could set 2 and/or 9 to "LEGACY/ISA"-- at least, that's how it often works.

[Great Hierophant]

I am very sorry to hear that, yours is a cool site too.  Keep on the lookout for a replacement of some kind.  CM-32Ls are more prevalent in Japan.