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Subject: Re: [korgpolyex] Re: Missing Joystick board (KLM-599) "mod"

From: Michael Hawkins <korgpolyex800@...>
Date: 2009-02-19

I haven't had a chance to take a long, hard look at the joystick circuit yet.

But I can tell you from memory that there are a bunch of op amps on that little board.

So there's a bit more going on than just two pots.

And I think from memory they are related to the pitch bend depth slider pot.

So my idea was to patch two -5 thru +5 voltages directly onto the demultiplexer inputs thus bypassing all of that. And I chose -5 to +5 because it wouldn't hurt to have the range go negative but I believe that 0V thru 5V should do it.

And I am very disappointed that it didn't work.

If I were you, I would try to find a replacement joystick unit.

The range of the joystick with the bend depth pot set to max is about 7 semitones (or half an octave up or down).

I still think that a range of 0V to +5V on those two pins should do the job. I am rather mystified as to why that wouldn't work.

There might be something else broken here. Do you have any knowledge as to why the joystick unit was missing in the first place?

Maybe somebody tinkered around and fritzed the demultiplexer to which the joystick output goes.

Mike.

From: serotonic_sound <sero-tonic@...>
To: korgpolyex@yahoogroups.com
Sent: Wednesday, February 18, 2009 8:28:36 PM
Subject: [korgpolyex] Re: Missing Joystick board (KLM-599) "mod"

> Zoinky is right that we need to use linear pots. What are all of the
> markings on your pot's? When you move the pots through their full
> rotation, does the voltage move smoothly or does it move slowly and
> then at each end, suddenly jump up or down?

The pots I have are new 10K linear pots and they indeed look/feel
linear when I measure them on my voltmeter. I think all they say is
"10K B" somewhere but I don't have them in front of me right now.

When I sent 0 to 5V through the pitch bend (1-5B). The pitch bend
went from down a fifth to normal at 12 o'clock, but did nothing for
the rest of the range. This happened with +5 connected, the wiper
connected to 1-5B, and either ground or -5V to the other side. And it
did feel "smooth/linear" from far left to 12 o'clock.

What is the range (in musical terms) of the joystick?

Thanks for your help you guys.

-Tim

--- In korgpolyex@yahoogro ups.com, "Gordon J. C. Pearce MM3YEQ"
<gordon@...> wrote:
>
> On Wed, 2009-02-18 at 05:40 -0800, Michael Hawkins wrote:
> > Tim,
> >
> > I recommend you wait until we have a bit more discussion about the
> > operation of the joystick board.
> >
> > I wouldn't want to see you blow your Poly up.
> >
> > I am quite busy today, but will attempt to provide some additional
> > instructions tomorrow.
> >
> > Zoinky is right that we need to use linear pots. What are all of the
> > markings on your pot's? When you move the pots through their full
> > rotation, does the voltage move smoothly or does it move slowly and
> > then at each end, suddenly jump up or down?
>
> The pots are a bit funny, with a kind of centre-tap on them.
>
> As far as the output from the joystick board goes, there are two
> connectors - CN1B and CN8B. CN8B goes to the bend range slider, CN1B
> goes to CN1A on the main board. CN1A is as follows:
> 1 - +5v
> 2 - 0v
> 3 - -5v
> 4 - X output
> 5 - Y output
>
> The X and Y outputs are centred around 2v, and go from 0v fully right or
> up to 4v fully left or down.
>
> I haven't drawn out the circuit on the joystick PCB yet, but I suspect
> it's some sort of voltage regulator and biasing thing.
>
> Have a look at the circuit below for an idea of what might work.
>
> http://www.gjcp. net/synth/ joystick. jpg
>
> Gordon
>