Brother PT 1800 - P-Touch 1800 Thermal Transfer Printer, Service Manual

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III - 11
3.2.7 Voltage Detector Circuit and Temperature Sensor Circuit
Figures 3.2-12 and 3.2-13 (See next page) show the voltage detector circuit and the
ambient sensor circuit, each of which is composed of a resistor network.
[ 1 ] Voltage detector circuit
This circuit, which is composed of divider resistors R8 and R9, steps down the power
source VBT fed from batteries or the AC adapter output and feeds the output to the A/D
input port PA1 on the CPU. According to the drive source voltage, the CPU determines
the optimum head drive power.
At power ON:
• If the voltage level of the VBT rises over approx. 15.1 V or drops below approx. 6.9 V,
the CPU immediately shuts down the power.
During non-printing:
If the voltage level of the VBT drops below approx. 6.9 V, the CPU immediately shuts
down the power.
During printing:
• If the voltage level of the VBT drops below approx. 6.4 V, the CPU displays the
following message to warn you of a low battery after completion of printing.
UK/BELGIUM version: "BATTERIES WEAK"
FRENCH version: "PILES USEES"
GERMAN version: "BATTERIEN SCHWACH!"
• If it drops below approx. 6.0 V, the CPU interrupts the printing and displays the
following message to warn you of a very low battery.
UK/BELGIUM version: "REPLACE BATTERIES!"
FRENCH version: "REMPLACER PILES!"
GERMAN version: "BATTERIEN WECHSELN!"
• If it drops below approx. 5.8 V, the CPU immediately shuts down the power.
• If it rises over approx. 15.1 V, the CPU displays the following message and
immediately shuts down the power.
UK/BELGIUM version: "WRONG ADAPTER"
FRENCH version: "CHANGER ADAPTATEUR"
GERMAN version: "FALSCHER ADAPTER"