Philips CDR880 - Power Supply Circuit Diagram; Detailed Power Supply Schematic

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MEASUREMENTS DISPLAY PANEL
1, Measurement of voltage supplies.
Several voltages arrive at the display PCB.
Measurements and limits.
Voltage
VFTD
VDC1-DC2
Vb
2. Measurement of oscillator.
As clock driver for the display controller a resonator of 8Mhz is used.
The clock frequency is available at pin 8 of the display controller.
Check the frequency of 8Mhz +5%.
3. Checking the control lines.
There are several lines which are inputs to the display controller and others which are outputs,
these lines have to be checked to guarantee basic functionality.
RESETN:
This line should be kept low during power up for at least 3 machine cycles,with supply voltage
within the operating range and oscillation stable.1 machine cycle = 12 X 1/Fe (8Mhz) Sec.
SDA and SCL:
The level on these two lines must be checked. When there is no communication they should have
the ‘High’ level.
INTERRUPT:
The interrupt line is an output for the display controller. Check if this level is high after reset, no
key pressed and no RC5 coming in.
Key matrix lines:
Check if at 1/O port 4 of the controller all pins are high.(No keys pressed).(Pin 26 to 33). If not
check respective pull-up resistors.
4. Operation of grid and segment control lines.
PM3392A
This figure shows the signal generated by the
display processor on one of the grid lines. The
level on the grid line changes from -26V to +5V.
The grid lines are scanned successively about every 950 psec.
PCS 83 985