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Service Guide ML390/391
Chapter A Board Diagrams
A.2.01 Control Board (SKRB) - Rev A and B
Function
The control board contains the microprocessor and its peripheral circuits. The drive circuits, paper end
sensor, and the interface connector are on this board. The 3.25 V lithium battery on this board provides
power to the EEPROM. This allows Menu Data to be retained when power is removed from the printer.
Firmware
Q5 and Q12
Fuses
Rev 1 and 2
F1: Thermal Fuse (The fuse is located on Q10.)
Rev 3 and up
F1: Inline Thermal Fuse
Jumpers
SP1 Q5 ROM Selection
Side A 512 kbyte
Side B 1 Mbyte
SP2 I-Prime (Host Reset) Selection
Side A I-Prime active with negative strobe
Side B I-Prime active with positive strobe
SP3 Auto Feed Select
Side A Auto Feed disabled.
Side B Auto Feed enabled.
SP4 Selection of application of +5 vdc to pin 18 of the parallel interface connector
Side A + 5 vdc applied
Side B + 5 vdc not applied
Sensors
Paper End
Switches
SASF
Test Points
Refer to the diagram
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