In order to change from high to low, the input must
be above VTHH. On the other hand, for the outpur to
turn from low to high, the input must be below VTHL.
For the
PC·1600,
three
resistors
(Rl,
R2, R3) are
chosen to for maintain
(b) level is in between VTHH
and VTH L under the normal state,
®
When the input (a) changes from low to high, the signal
(b) is sent to the VDD side as a pulse above VTHH by
means of the capacitor
Cl between
VTHH and GND
as a normal level. As a result, the signal (c) changes
from high to low.
@
On the other hand,when
input (a) changes from high to
low, the signal (b) is sent to the VEE side as a pulse
-
PC-l600
above VTH L by means of the capacitor
Cl between
VTHL and GND. As a result, the signal (c) changes
from low to high.
A signal transition
is latched on the output
side using
the pulse by means of the capacitor and characteristics
of the Schmitt
IC for conversion of a logic signal into
the RS-232C interface siqnal.
The role of the R4 output
is to prevent the possible
destruction
of the
IC4584 which
may occur by an
accidental short in connection
with the RS·232C inter-
face or the connection
of outputs together.
The capacitor
C2 is for increasing speed for conveying
a change in the MN4584.
8.
Service precautions
Before servicing of the PC-1600, lt is mandatory
that you
release static power in your body by using the earth band.
(When removing the key PWB from the top cabinet, it is
recommended
that
you secure
the keytops
and display
filter using cellopane tape.)
In order to open the cabinet, remove the RS-232C interface
connector
cover, system
bus connector
cover, expansion
slot covers
(1, 2), battery
cover, batteries,
and the ex-
pansion module.
Remove the five screws (see figure) and slowly lift the
bottom
cabinet with care so that you do not damage the
chips installed on the FPC PWB.
Fig.8·1
-15-
Now, you will see the signal levels. To get power by using
the AC adaptor
or battery
cells, connect
the oscilloscope
probe to the negative side of the battery.
Fig.8-2
8-1.
Replacing the FPC PWB
1. With the connector
PWB secured on the bottom cabinet,
pry the holder
(A) at (A) using a flat tip screwdriver.
Next, remove the holder (B).
Bottom cabinet
Holder (A)
Holder (B)
Fig.8-3
Summary of Contents for PC-1600
Page 42: ... 11 CIRCUIT DIAGRAM PARTS POSITION KEY P W B LCD SIDE 39 ...
Page 43: ...PC l600 40 ...
Page 44: ...PC 1000 KEY P W B LSI SIDE 41 ...
Page 45: ... 42 ...
Page 48: ... PC l600 F P C P W B 45 ...
Page 49: ... Kn 46 ...
Page 52: ... PC l600 CONNECTOR P W B 49 ...
Page 53: ... 50 ...
Page 55: ... __ PC l600 tli I ONLY Pc 1600K I I 1 I 52 l J ...
Page 56: ... PC l600 K MEMORY P W B ROM Cut c IJ O lJ1F C O lJ1F I Bend capacitor to inward ROM SIDE 53 ...
Page 57: ...RAM SIDE 54 ...
Page 61: ...I I 2 3 4 42 58 ...
Page 93: ... P W B LSI SIDE t 90 ...
Page 117: ... PC I600 ...