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Power Supply Board (M1353-66502)
Chapter 6 Theory of Operation 55
Power Supply Board (M1353-66502)
The Power Supply Board operates as a linear regulated power supply with rectifier, capacitor
and regulator. It generates the following voltages:
Regulated dc:
±12V, +5V and +24V
Unregulated dc: +7V to +12V
±12V and +5V have an electronic short circuit current limit. The +24V dc regulator works
independently from the others. The +24V are used for the thermal printhead fed through
the recorder IF-board. The internal +2.5V reference voltage is generated from the +24V, so
if the 24V section is inoperative, the rest of the power supply won’t work. The -12V
regulator also needs the regulated +5V to work correctly. The reset (open collector output)
is active low, when either the +5V is lower than +4.6V or the +24V is lower than +14.8V. If
the +5V is higher than 6.2V (this can be caused by any failure of the power supply or the
other boards) the over-voltage protection is triggered and pulls down the voltage to about
3.4V. This state can only be relieved by switching the monitor off and on (if the failure isn’t
still remaining).