Sharp PC-1600, Service Manual

Page: 71 / 118

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PC-1600
4. CMT interface
The CMT interface consists of the following circuits:
• Write circuit
• Read circuit
• Remote circuit
4-1. Write circuit
As shown below, the logic level signals are converted into
signals of micro level.
• High frequency component of signal is eliminated. ~
ILow pass filter I
• As a 3KHz component drops 6dB than a 1.5KHz com-
ponent because of the low pass filter, compensation is
therefore done.
~lBfU!1
frequency compensation I
• The
outout
level is
set
to the micro level. ~IAttenuation I
• DC component is cut. ~~~~
CMTOUT
4.7VPP
=
vcc
L"..IU1Il
N\I\~
~.5mvpp
• Low pass fi Iter
• High frequency
compensation
• Attenuation
• OC decoupling
MIC
3mVRMS
Rl C2
CMTOUT~7µF
Cl
R2
MIC
6.8Kn
R3 ~ 680n
~~~
Low pass High Attenuation
filter frequency
compensation
Cl, C2: DC decuppling
Output level: 3mV rms
Output impeadance: APROX 600n
4-2. Read circuit
1MU
EAR
I
I
CONTRO
L
..J
Inside gatearray
The read signal amplifier circuit consists of the same type as
that of the CE-150. The circuitry is contained inside the
gate array in the case of the CE-1600P.
4-3. Remote circuit
For the relay (AG8229 or G5AK-287P) is a two-coil
latching type, A ON (or OFF") pulse must be given to the
activate (or deactive) the relay through the driver of the
gate arrav, in order to turn the relay active. (See Fig.8.)
The width of pulse must be more than 5 milliseconds than
that mentioned in the relay specification. With the CE-
1600P, it is set to about 10 milliseconds.
The following signal formats are used for the cassette
interfacing signals.
Write PWM method (1600 method)
Read PWM method (1600 method) and
1500 method
5. Power supply circuit
5-1. Power supply
VP, VBAT, and battery recharge circuits
01
RM-l0Z (x2)
02 03
AC Adaptor
About 8.4V .. "
liIoI ~ , ..
VP (6.4V)
RK-13
AAx5 : D6
11OQ03(lA) x
2
1
For prevention of reverse current to the rechar-
geable battery to the adaptor.
To achieve efficient recharging of the batterv, a
Schottky barrier type diode R K-13 (1.7 A) is
used.
02,03: These diodes are used to drop the voltage from the
printer to less than printer driving voltage (7.15V
01 :
04:
max.).
F or prevention of reverse current from VP to the
rechargeable batterv, when the adaptor is being
used.
For prevention of reverse current from V BAT
(PC·1600) to VP (printer).
The diode is a Schottky battery type for avoiding
battery exhaustion when the adaptor is used,
To avoid exhaustion of the battery in the main
unit when the rechargeable battery is used, 06 is
used to bypass 04 and 05.
To meet the printer drive voltage (5.0V, min.), the
rechargeable battery low voltage is set to 5.65V
lirnit (1.13V per batterv l.
After the main unit battery is ORed with the VBAT supply
from the CE-1600P, VCC is regulated to 4.7V before
supplied to the CE-1600P. (See the figure below.)
When the main unit power is turned off, VCC is not sup-
plied.
05:
06:
CE-1600P
PC-1600(Main unit)
VCC4-~r------r----------------~
vcc
±
UM-3
1;
(x4)