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  #1  
Old 11-03-2009, 09:42 PM
nickca nickca is offline
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Default Strange problem with UMR and SK-1

I'm trying to install a UMR in my SK-1. I simply cannot get any MIDI activity to register. Here's what I've done:

1. Checked, re-checked and re-re-checked my MIDI cable wiring (pins 4 and 5). It's correct. I also tried it backwards just to be sure.
2. I replaced the optocoupler with a known working one. I connected an LED probe across pin 6 of the optocoupler and ground and sent a long SysEx message. The LED flickered, so MIDI is getting in past the optocoupler.
3. I've checked and re-re-re-checked my data/select cable wiring. It's correct, and the keyboard still works so there's no loose pins.
4. My DIP switch settings are exactly as specified on the SK-1 installation guide, and SW2 is set for channel 1.
5. Just to be sure, I re-soldered over every joint just in case one of them was cold. No joy.

Now, the weirdness, besides no MIDI response:
If the UMR is off but the SK-1 is on, the power and activity light flicker. I have other stuff (a VCF and a CV summer) connected to the internal 7.5V rail (the audio amp power rail, not the battery terminals), and the UMR is using the 5V rail and the same ground. Is there only one ground in the SK1, or have I mis-wired the ground? My SK-1 is slightly different than the one in the guide, so I had to find the points with a multimeter, but the UMR gets a steady 5V (actually more like 4.6V) when turned on.

Also, I forgot to wire in all but one of the pads of the upper-right resistor network the first few times I applied power. Could I have damaged something? As I stated, I replaced the optocoupler, and that was afterwards, and the microcontroller still lights the activity LED briefly at powerup, which I assume means it is not fried.

Please help, I know this is a tough one but I don't know what else to try. I suppose I could try disconnecting every addon but the UMR, but that's a bit of a pyrrhic victory, and I don't know why that would break it.

Last edited by nickca; 11-03-2009 at 09:45 PM.
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  #2  
Old 11-03-2009, 10:16 PM
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Are you using the power connections (+5V and ground) exactly as shown in the UMR/SK-1 installation instructions?
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  #3  
Old 11-04-2009, 12:15 AM
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As I said, my board appears to be slightly different (I know there are different board revisions), so the connection points aren't exactly the same. The 5V point is in almost the same place, but the ground point isn't. I've connected ground to the same ground the audio amp is using, which I've also grounded my other addon boards to. I'll double-check the wiring, though. Would taking the 7.5 supply through a 5V regulator be worth trying as well?

So is the power/activity light flickering when off normal? I'm guessing it's not. A ground loop maybe?
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  #4  
Old 11-04-2009, 12:49 AM
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I'm sorry, I was wrong, the same 5V and ground points are on my board. I had the 5V point right, but the ground point was a point further along the same ground rail. I didn't think it would make a difference, and it didn't, but I rewired ground to that point. Still getting the flickering and still no MIDI. I also tried disconnecting my other boards from the 7.5V and ground rails, but that didn't fix it either. It seems like the MIDI signal is getting to the microcontroller, then doing nothing. The activity light lights up on powerup though, so it must not be broken.
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  #5  
Old 11-04-2009, 03:14 PM
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Does the SK-1 keyboard work normally?

What are your SW2 switch settings (please report the state of each position)?
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  #6  
Old 11-04-2009, 03:17 PM
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Quote:
Originally Posted by nickca View Post
So is the power/activity light flickering when off normal? I'm guessing it's not.
The UMR may receive power, even when the SK-1 is powered off. So this is not anything to be concerned about.
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  #7  
Old 11-04-2009, 08:05 PM
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Yes, the SK-1 keyboard works fine, and all the connections from the keyboard's ribbon connector to the UMR are solid. As for SW2 settings, I've tried pretty much all of them. Currently it's set for channel 1, or off-off-off-off.
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  #8  
Old 11-04-2009, 08:06 PM
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Are there any voltages I can check on various microcontroller pins to make sure they're correct?
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  #9  
Old 11-04-2009, 08:23 PM
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Quote:
Originally Posted by nickca View Post
Yes, the SK-1 keyboard works fine, and all the connections from the keyboard's ribbon connector to the UMR are solid. As for SW2 settings, I've tried pretty much all of them. Currently it's set for channel 1, or off-off-off-off.
Ok. Keep in mind that the channel change only takes place when the UMR is power-cycled. Since it will leech power from even a switched-off SK-1, power-cycling will involve disconnecting the "+5V" terminal on the UMR.

Please try this:

Temporarily disconnect (or install a switch in) the line from the "+5V" terminal of the UMR to the SK-1. Then power up the SK-1, and wait a few seconds. Then, reconnect the +5V to the UMR. Does this will make a difference?

Also, what device are you using to send MIDI? Can you capture the output from the device, so that we're sure the note numbers/channel are what we're expecting?

Can you post some photos of your install? Doing my best to figure it out...
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  #10  
Old 11-04-2009, 08:42 PM
nickca nickca is offline
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I have a switch installed in the +5V line going to the UMR, and I turn the SK-1 on, then the UMR. However, the power and activity LEDs will flicker when that switch is turned off (that's what I meant by "if the UMR is off and the SK-1 is on). When I turn it on, it comes up as normal.

I'm going to try the separate 5V regulator thing, because something in the other mods I've done seems to be screwing up the onboard 5V source. Here is exactly what happens:

1. The SK-1's soft on/off switch is set to "off" (I don't have a hardware ground-disconnect on/off switch, just the normal SK-1 soft on/off) and the UMR's 5V line switch is off. In this state, nothing happens.

2. I turn the SK-1's switch to "play". At this point, the UMR begins flickering, even though the 5V line is disconnected by the switch.

3. I turn the UMR's switch on. The UMR appears to boot normally (power LED comes on, activity LED lights for a second or two)
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Old 11-04-2009, 08:46 PM
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Wait a minute... if the 5V line is disconnected (by the switch), leaving only ground, how the hell is it getting power at all?!? Something is very weird here. I'll try just disconnecting 5V completely and see what happens as well.
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  #12  
Old 11-05-2009, 08:52 AM
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OK, I've tried:

1. Powering the UMR via the 7.5 rail through a 7805 regulator. Same thing: flickering LEDs (there's an oscillation between about 2 and 3.5 or so VDC across the UMR's power terminals when the 5V line is switched off).

2. Powering the UMR via an entirely separate 9V battery. I didn't measure the voltage, but the flickering was less bright yet still present.

In both cases, this is when the SK-1 switch is in the "play" position and the UMR's 5V line is switched off. When I switch the UMR on with the SK-1 on as well, it appears to power up as normal and gets a steady 5V.

As far as what I'm using to send MIDI, I've tried a virtual keyboard from my Mac's MIDI interface, and my MIDI controller (a homebuilt Midibox64). I'm sending a G2 note, which should be within the UMR's range. I also have an Oxygen-8, but really I don't think the sending end is the problem.

At this point I've given up. If you've nothing further I can check, could we possibly discuss an installation service price for installing a kit I've already completed? Or if you suspect the microcontroller may be bad, how I might go about getting a replacement?
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  #13  
Old 11-05-2009, 08:54 AM
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Also, I tried disconnecting everything but the UMR (i.e. my additional addon boards), so it was as if I was installing the UMR in a stock SK-1. This caused no change whatsoever, so it isn't being caused by my addons (a Tim Escobedo style resonant filter and a simple opamp CV summer to feed envelope CV to the filter).
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Old 11-05-2009, 03:30 PM
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Quote:
Originally Posted by nickca View Post
As far as what I'm using to send MIDI, I've tried a virtual keyboard from my Mac's MIDI interface, and my MIDI controller (a homebuilt Midibox64). I'm sending a G2 note, which should be within the UMR's range. I also have an Oxygen-8, but really I don't think the sending end is the problem.
Ok. Have you tried other notes? MIDI octave #s are note standardized, so on some controllers, G2 could be below the range of the UMR.

Can you post some photos of your installation?
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  #15  
Old 11-05-2009, 07:58 PM
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Yes, the first thing I tried was a virtual keyboard on my Mac that can send the entire MIDI range, and I was trying all different notes. None made it through. I just programmed my Midibox to send a G2 note on channel X when I press button X, where X is 1-16, so I could easily test if it was a channel problem. I've tried all kinds of MIDI notes on every channel.

I can post photos of my install, but I'm not really sure what you could glean from them. Everything is hooked up with the same color wire, and it would be hard to tell in a photo what goes where. I'll take a pic anyway, though.

Here's what I'm starting to suspect: I noticed that when I hit a key and the UMR is off, the power LED flickering changes slightly. I have the envelope CV points of the four voices connected together to a CV summer, which feeds the VCF. I have tried disconnecting the summer and VCF from power, but I haven't tried disconnecting the four CV points. Maybe having them connected together to the summer (they aren't shorted together, though: the summer just mixes them via resistors then attenuates the signal with an opamp) is screwing with the UMR?

The ~3V oscillation across power and ground when power is disconnected and ground is connected is beyond my understanding of electronics. Anyone know what the hell's going on there? I'm not even sure how that's possible. And that happens, remember, even if I've disconnected all my other addons leaving essentially a stock SK-1.

Edit: I haven't mentioned so far, I also installed the common SK-1 internal filter bypass mod (the "Stikka" one, it involves cutting a resistor and adding a 1K resistor), but that's all in the audio section and I'm not sure how it could affect the UMR. However, that could be the problem for all I know.

Last edited by nickca; 11-05-2009 at 08:07 PM.
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  #16  
Old 11-06-2009, 02:57 PM
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I don't think it's a cause for concern that the LED flickers when the UMR power line is disconnected. The UMR can get a small amount of power from the select signals of the keyboard matrix... I have sent a PM to you.
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  #17  
Old 11-08-2009, 12:08 AM
nickca nickca is offline
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As requested, a photo of my install. I've used only grey ribbon cable wires everywhere, so it's a bit hard to tell what's where. You can see the jack, activity LED and 5V switch taped up in a little bundle. I suppose the only thing you could tell me is if I've somehow wired the data/select cable backwards, although I wired it according to the numbers on the SK-1 PCB. The red wire on the ribbon cable is wired to pin 1 (I'm fairly certain) on the SK-1.

http://nickca.com/misc/IMG_0024.jpg
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  #18  
Old 11-10-2009, 02:59 PM
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Can't see anthing there that is an obvious problem--thanks for your patience. I have sent another private message to you.
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  #19  
Old 11-13-2009, 05:48 PM
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I'm happy to report that I received the replacement and it worked the very first time. I have no idea why the other one didn't work, but it was probably either my fault or a weird fluke (it was definitely NOT a MIDI config problem). Thanks for replacing it, a lot of people would have said "screw you, you probably broke it, buy another", and that would have even been fair. I'll be buying MIDI kits for my VSS-30 and Speak & Spell from here in the future for sure, and recommend the UMR product to anyone.
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  #20  
Old 11-13-2009, 05:59 PM
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Also, the LED flickering I kept mentioning - totally normal. It does not indicate a problem.
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