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Old 06-15-2009, 08:48 PM
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Default VL-1-MIDI Issues

J. writes:

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I finished installation of your midi circuit into my VL tone today and I ran into a few issues. While noting the calculator mode problems discussed on your board, I chose to resolve this problem by finding an alternative point with 3V on the board that would supply in calculator mode and use a separate power switch for the midi circuit. While the midi circuit is indeed getting power in calc mode, the VL tone is unresponsive and appears to be off. In record mode, the unit functions erratically and makes screeching noises and in play mode, if the midi circuit is powered down, some local keys are unresponsive and the unit acts unpredictably. The later issue isn't a big deal, maybe it's even expected, but getting calculator mode and record mode to work is pretty crucial.
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I experimented in giving the midi circuit it's own power supply today and I have run into the same issues. How exactly does the midi circuit disable the keyboard anyway? There has to be a work-around for this...Perhaps you could explain with some detail as to how the midi circuit disables the local keypad. Maybe there is a switch or a series of switches I could install to cut the midi circuits connections to the vl-tone to retain stock usage of calculator/adsr mode. Any help would be greatly appreciated.
I have to admit that I do not know exactly why the the VL-1-MIDI would cause any loss of functionality in, say, calculator mode vs keyboard mode. I apologize--I do not have a VL-1 on hand with which to test, so I'll only be able to send some ideas your way.

In theory, the VL-1 simply injects keypad signals to the buttons of the VL-1, and when no MIDI notes are active, there is not any impact on the VL-1 operational state.

I think the first troubleshooting step should be to partially disconnect the MIDI board from the VL-1, power everything up, and see which connections are causing the VL-1 to become disabled.
  1. First, leave all of the power & "Data Out" connections in place, but disconnect the "Select In" terminals.
  2. Second, leave all of the power & "Select In" connections in place, but disconnect the "Data Out" terminals.

Both of the steps above of course will eliminate any MIDI functionality, but we can see whether it's a data line (or two) or a select line that's causing trouble.

I strongly suspect that the first option above will return the VL-1 to normal functioning. After thinking about it, I believe that it may have to do with the "pull down" resistor connected to each "Select In" terminal on the MIDI board...parts RN1 and RN2 are each 10k-ohm resistor arrays that pull the select signal down to ground (in theory) when there is no select activity generated by the host machine...perhaps they are altering a select signal in a way that the mode setting / overall functioning is impacted...

So perhaps removing RN1 and/or RN2 will solve the problem. Can you give this a try?

If that doesn't work, but I was correct about option (1) above alleviating the problem, then we can work on isolating which exact select line(s) may be causing trouble and continuing from there.
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Old 06-15-2009, 09:45 PM
jordan s jordan s is offline
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Thanks for the great info. As soon as I get some time, I'm going to try out your suggestions and I'll post my results. My solder sucker is ready for action.

Jordan
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Old 06-17-2009, 08:43 PM
jordan s jordan s is offline
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So I partly understand what was going on and I am partly still mystified. After removing all the Select connections, I was running into the same problems. I then realized that the screen was not working at all. The plastic ribbon connector was attached but the actual piece that makes contact with the LCD screen was not touching the contacts at all. I'm not sure how it worked in the first place because there is no means of holding the plastic strip it firmly against the LCD contacts. I found that if I wedged some matchsticks in there and firmly screwed the board on over it, I could get the contacts to touch and retain about 90% visibility of the screen. I don't know why, but after that, everything worked perfectly. I was able to reconnect the Select lines and it all works very well with the alternative internal power source I was previously using. I have attached a guide that shows my points that should give about 3v. Keep in mind that voltage is always present, even when the keyboard is switched off, so a switch needs to be run in series with one of these points to the board. This is essential for being able to use calc/adsr mode as using the voltage source in the build guide renders the local keypad disabled in calc mode.

You could say that perhaps the calc/adsr mode worked before but I couldn't tell because the screen wasn't working. This might be the case, however, record mode was making screeching noises and acting erratically but it is fine now that the screen is working. I can't really explain this, I'm just glad it's finished and everything works. I'm going to make a new thread with photos and info about the enclosure I used very soon. Thanks to John for the friendly support and a great product.



Sorry about the bad quality image, I stole it from someone else. The connections are both on the leads of stock resistors. The pink dot is +V, the green dot is Gnd. Keep in mind, that I don't want to open my vl-tone up again and this guide is from memory so make sure to test these points with a meter first.
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Old 06-17-2009, 08:52 PM
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Awesome, I'm glad to hear that things are working. Thanks so much for posting your results/methods--this type of information is really valuable for other users.
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