Melody Circuit.12 - Casio SK 8A Service Manual & Parts List

MELODY CIRCUIT
VD -
p 'f O
VDo-,
15K
15K
_
111
_ 1
n
L5
rev
Js 1
ID
CD
O
li
<XO-7-.MA—O
I
- AAA-1—W—(I—C
68 K 18|
\
2.5 V
Mixer
47 K 11
Amp.
2.5V 220K
47K
Gain Controller
Envelope ^11 Me'°?V or
5^—,-
4
'
Obbligato
| t 3 Pitch SE
-II-
14 Envelope EE
(
—
I ^
r
Pitch
SF
-it-—-——-i
Envelope EF U^0'
--iJ Ch0rd
Envelope
CPU outputs four each of pitch and envelope signals.
Normally all the signals are for melody sounds however, when a ROM Pack music is played, each
pitch and envelope signals become obbligato, bass, chord, or melody sounds.
CA91A 02 contains four mixing amplifiers and merges each pitch and envelope signals.
Gain Controller balances the sound volume of melody and accompaniments for ROM Pack musics.
Signal K014 normally stays HIGH level so that all the switches turn on. When a ROM Pack
music is played, K014 falls to LOW level turning the switches off and all the accompaniment
signals are reduced as they pass through the resistors.