Service Manual Ponygraphic
Chapter 3
Part Description
3.4
(7) RS232
The serial communication is completely managed by the CPU; the only external component is
U11 (MAX233) which does the voltage level conversion from TTL (0-5V) to RS232 (-12+12V).
The protocol used is the following:
Data
bit: 8
Parity:
none
Baud
rate:
4800
Handshake:
DTR
Hardware
(8) Power
Supply
The power supply to the Pony graphic Unit and the Optoelectronic transducer is done by 4
rechargeable NiCD batteries (1.2V, 1.2Ah).( they are packed in set of 2 ,each set containing
two batteries)
The IC U14 (MAX761) regulates the supply Voltage of the digital components. It also detects
the Low battery status when the battery voltage goes lower than 4.7 Volts.
The IC U12 (MAX635) generates a negative voltage of -18 Volts (pin 11) in order to power the
LCD Display contrast.
The LCD back-light power supply is controlled by software (battery saving mode) and
generated by an switching circuit composed by T1, C32, C33, R33, R34 and Q10; the supply
voltage is about 90 VAC RMS.
The battery voltage directly powers the Optoelectronic Transducer and the Printer.
The IC U10 (TEA1100) performs the battery charging management. The NiCD batteries are
charged with two different levels:
Fast charging:
800mA (front panel green led fix)
Slow charging:
15mA (green led blinking)
The circuit Switches from fast to slow charging when one of the following conditions is verified:
•
Battery fully recharged (Voltage Decrement CutOff System; the battery voltage is
continuously monitored by pin 7, when a decrement is detected TEA1100 switch to
slow mode).
•
Battery temperature higher than 45°C (the temperature is monitored by thermistor RV2)
•
Battery voltage lower than prefixed threshold
•
Battery Voltage higher than prefixed threshold
•
Charging time higher than 2 hours.
3.2.3. Adjustments
&
checks
There are no adjustments to be performed on the motherboard.
3.2.4. Assembly
Drawing
3.2.5. Warnings & Indications in Event of Failure.
•
The system does not operate when switched on (refer to Troubleshooting section)
•
Printer / serial communication does not work
RTC
BATTERY
I/O
FPGA
RA
M
EPR
O
M
U1 micro controller
RS 232
U12 Display control
