VL-1-MIDI with ADSR programming

[John]

A customer writes:

Everything seems to be working fine, but there appears to be one rather serious bug in the design that I could use a workaround for.

The VL-1 is prized because it's one of the only one of the series to allow ADSR programming. This is done by putting the keyboard into "Calculator" mode, hitting 8 digits, storing them in memory and then switching back to "Play" mode/ADSR to hear the results. However in Calculator mode, the light on the MIDI board goes off and I cannot enter numbers on the local keyboard. I suspect this is because the synth is shut down when the switch is set to Calc. But the primary reason to have a VL-1 is to get the ADSR mode, so this is a rather major loss.

Perhaps there's already a workaround that I haven't found yet?

I wasn't aware of this problem. I think you are correct--switching to calculator mode must cut power to the MIDI board, which disables the keypad.

I think a simple workaround would be to find an alternative connection for the positive power lead of the MIDI board. If you have a multimeter handy, I think you can find two different wires on the ribbon cable (where the GND and +5V connections are) that supply about +3V (the UMR board is operating on about 3V in this case, despite the 5V label). One of the 3V lines switches on & off with the synth, but I think the other does not. If the latter is used, the UMR should not shut down when calculator mode is selected. This may fix the problem.

If this fixes the problem, you'll also want to install a switch in the power connection, so that you can manually turn off the UMR board. Then the VL-1 batteries will not be drained when not in use.

Please let me know if this was helpful. :)

[greysound]

For a variety of reasons, I opted to power the Highly Liquid card with its own power supply instead of off the VL-1. (I have other additions that I'm making that draw power, so why not?)

Seems to fix the problem. I now have calculator mode, which means I have ADSR mode.

As a hint to other VL-1 builders, I found that the best way to make the PCB connections was to route wires through the unused holes in the back of the PCB and then to the individual spots that need connections. It's not as pretty as running a ribbon cable, but a ribbon interferes with the button operation.

If you're careful, using as little solder as possible (and using solder with a tiny diameter), you should be able to make the connections in under 2 hours.

Thanks again for the awesome kit! Very impressive.