Akai GX-M10

4. OSCILLATOR CIRCUITRY FOR REC
TIME COUNT (Refer to Figs. 10 and 11)
This circuit is to indicate the Rec Mute Time Count
in Program LEDs -and to add one second interval
pulses to the UP IN terminal of IC2.
When the Rec Mute button is not depressed, IC3a’s
input terminal @3 is “L” and IC3b’s output terminal
@ is “L”. C13 has been discharged as in Fig. 10 and
1C3a’s input terminal @ is changed to “H” by this
potential.
At this point, when the REC MUTE switch is
depressed, IC3a’s @3 changes to “H” IC3a’s output
terminal @D to “L” and IC3b’s @ to “H’”. As IC3’s
@ has become “L”, C13 discharged through R44.
During this discharging period (time constants of C13
and R44) IC3’s @ becomes “H” due to the voltage
drop at both terminals of R44.
Once C13 has finished discharging, there is no current
flowing in R44 and the voltage drop is 0 so IC3a’s
@ changes to “L”. As a result IC3a’s @) becomes
“H”, IC3b’s GO “L” and this time the charging
current flows from IC3a’s @) throught R44 to C13.
During this charging period (Fixed time constants
of R44 and C36) IC3a’s @) becomes “L”.
After C36 has been charged, due to this potential,
IC3a’s @, changes to “H”, @ to “L” and IC3b’s
@ to ‘“H’’. The above operation is repeated and a
1 Hz square wave appears at IC3b’s output terminal
®
. MONOSTABLE MULTIVIBRATOR
OPERATION (Refer to Fig. 6)
A plunger is activated by IC2’s output © to release
the FF or RWD key in the IPSS mode. However in
IC2’s output there is a pulse width which is too
narrow to drive the transistor directly so the pulse
width is enlarged by a Monostable vibrator, the
transistor drive is corrected and then the plunger is
activated.
. ONE SHOT PULSE GENERATOR
(Refer to Fig. 6)
This circuit resets the counter for an instant when the
REC key has been depressed while the REC Mute
switch is being depressed.
When the REC key has been depressed after the REC
Mute key, if TR14 has not been attached, TR4 turns
off and the IC2 counter does not reset. If the counter.
is counting down numbers with the program switch
these numbers will. be increased by the time taken to
depress the REC Mute switch. To prevent this, when
the REC switch is put on TR14 is put on simultane-
ously for a certain period (the difference between
C70’s and C71’s charging periods) of time only.
When TR14 is turned on TR4 turns on and the
counter is reset. Therefore the REC MUTE TIME
indication begins from 0.
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