[sdiy] SH101 MIDI Mod problem

[Dave Magnuson]

Here's what I would do:

Hi Rob,

To help you diagnose the problem, first disconnect the CV line from the
MIDIJack to the SH101.

Hook it up to MIDI and send a C3 followed by a C4.  The 101 is V/Oct, so
try to verify that C3 from the MIDIjack output is 1V less than a C4, etc.

Doing this will tell you if the fault is in the MIDIJack or the 101.  It's
also possible that the MIDIJack is simply hooked to the wrong point in the
101.   I'd also check the powersupply connections to the MIDI board.  Make
sure that the V+ rail doesn't sag when it sends a gate, etc.

After you find out where the fault lies (MIDIjack or SH101), you can get
some more constructive help.  Do you have a schematic for the MIDIjack?  

Dave Magnuson



At 07:07 AM 7/31/02 -0700, rob wrote:
>Hi All,
>
>I have a problem with a modded SH101 that I'm hoping
>someone has some insight into, can possibly help.
>
>The mod I added was a Synhouse MIDIJack.
>
>With MIDI disabled, the synth plays fine from the
>local keyboard.
>
>When MIDI is enabled, the synth has a weird tuning
>problem that can best be described as very similar to
>portamento. That is, when I play legato C2 and then
>staccato C4 C4 C4 C4 --> with each successive C4, the
>pitch ramps closer and closer to C4, as if portamento
>was on.
>
>Obviously this makes the unit somewhat unusable for
>melody lines via MIDI.
>
>Does anyone know what to look for here? I don't have
>any gear with CV, but I do have a scope and meter.
>
>I can provide an mp3 example of the problem if that
>helps.
>
>
>Any help would be greatly appreciated!
>
>
>Rob
>
>
>
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