[sdiy] keyboard schematics

[Osamu (Sam) HOSHUYAMA]

Hello Fabio,

fmg wrote:
> Sam,
> 
> I'm looking at Moritas keyboard schematics of your site (moritaKB.gif)
> and wondering if you can help me with some questions.
> 
> 1. Do you know the value of the Rs in the voltage divider (or the
> numbers of keybrd contacts), or the value of zeners in both sides of
> this chain ?

That part is very typical with old monophonic keyboards.
I guess 100 ohm resistors are OK.

The value of zener diodes is not important here.  Upper side is just 
a voltage source and the lower is a current source.

The voltage defines the highest KB output, which should be determined
by the spec of the VCOs you use.

The current must be set so that the voltage across each 100 ohm is 1/12
volts.

> 2. What say the vertical text that point to the 4558 ? (the one which
> have the + input to the keyboard)

"Calculates the voltage of high note."

> 3. The output of the other opamp of this 4558, goes to the 10k of the
> 741 immediatly below the S&H buffers ?

Yes.

> 4. What say the text below this 741 and the S-T that follow it ?

What's S-T?

"Detects whether the number of pressed key(s) is multiple."

> Sorry to be so inquisitive :-) I saw the PE msonic rf keybrd, the
> moog 952, and the Morita's, and liked this.

Why do you need duophonic keyboard?
Morita's design requires a 2-contacts-per-key keyboard.
(The bottom left switch represents all the trigger contacts.)
Do you have one?

Regards, Sam Hoshuyama
-- - ---  - -- ------ - -------- -- - ---- -
Osamu (Sam) HOSHUYAMA      houshu at rogers.com
                              Ottawa, CANADA
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