Philips CDR570, Service Manual

Page: 44 / 59

Faultfinding Guide GB 44 CDR570/930 8.
8.1.2 Test instructions
Supply voltages
The display board receives several voltages via connector
1119 (and connector 1121 for CDR570/930).
•
VFTD : -38V
±
5% measured at pin 2 of conn. 1119.
• VDC1-VDC2 : 3V8
±
10% measured between pin 1 and 3 of
conn. 1119.
• +5V : +5V
±
5% measured at pin 10 of conn. 1119 (pin 4 of
conn. 1121 for CDR570/930).
Voltages VFTD, VDC1 and VDC2 are produced in the power
supply unit and sent to the display board via the CDR main
board. The +5V voltage is produced on the CDR main board as
D5V.
Clock signal
As clock driver for the display controller, a resonator of 8 Mhz
(1110) is used. The signal can be measured at pins 8 and 9 of
the display controller : 8 Mhz
±
5%.
Control signals
RESET
The reset signal comes via pin 4 of conn. 1119 from the DASP
master processor on the CDR main board (SYS_RESET). The
reset is low active. It should be kept low during power up for at
least 3 machine cycles with supply voltage in operating range
and a stable clock signal (1 machine cycle = 12 x 1/Fc (8 Mhz)
sec.). During normal operation, the reset should be high (3V3).
The high signal is 3V3 because the DASP operates on 3V3.
I2C DATA/I2C CLK
These lines connect to the DASP master processor via
respectively pin 5 and pin 7 of conn. 1119 (pin 5 of conn. 1119
and pin 1 of conn. 1121 for CDR570/930). When there is no
communication, they should have the high level (+5V). The
oscillogram below gives an indication of how these signals
should look like.
Figure 8-10 ‘I2C signals’
FTD drive lines
Filament voltage
Should measure 3.8V
±
10% (=VDC1-VDC2) between pins 1-2-
3 and pins 45-46-47 (pins 1-2 and pins 48-49 for CDR570/930)
of the FTD (1113).
Grid lines
Level and timing of all grid lines, G1-->G15, can be checked
either at the FTD itself or at the display controller. Grid lines
G13, G14 and G15 each have an extra current amplifier in line
: T7203 for G13, T7204 for G14 and T7100 for G15. A typical
grid line signal shows in the oscillogram below.
Figure 8-11 ‘Gridline’
Segment lines
Level and timing of all segment lines, P1-->P21 (P1-->P20 for
CDR570/930), can be checked either at the FTD itself or at the
display controller. The data on these segment lines however,
depends on the characters displayed. The oscillogram below
shows a segment line with data. A segment line without data
maintains a -38V level.
Figure 8-12 ‘Segment line’
Key matrix lines
The lines connected to pins 34, 35, 36 and 37 of the display
controller act as matrix scanners. Without a key pressed, they
maintain a low level. As soon as a key is pressed, the scanning
line connected to that key puts out a scanning signal, which
should look like the oscillogram below. This scanning signal
goes via the pressed key to I/O port 4 of the display controller
(pins 28 to 33). The display controller can now determine which
key has been pressed. Without a key pressed, pins 28 to 33 of
the display controller maintain a high level (+5V).
PM3392A
CH1!2.00 V=
CH2 2 V= MTB10.0ms ch1+
+5V
0V
+5V
0V
I2C DATA
I2C CLK
CL 96532076_025.eps
290799
PM3392A
CH1!10.0 V= MTB1.00ms ch1+
0V
+4V
-38V
CL 96532076_024.eps
290799
PM3392A
CH1!10.0 V= MTB1.00ms ch1+
0V
+5V
-38V
CL 96532076_027.eps
290799
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