AFP Imaging Mini-Medical Series, Installation, Operation & Service Parts Manual

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Service
Mini Med Series 0000061122
Service Procedure 5-4
Circuit Descriptions &
Calibration Procedures
WARNING: The following calibration adjustments are made on the Logic Board.
Since potentially fatal voltages are present and easily contacted, these adjustments
must be performed only by qualified service technicians.
Access to the circuit cards may be gained by removing the two mounting screws from
the underside of the feed tray, then lowering the control box door assembly.
All calibrations are done on the Logic Control Board located on the right side of the
opened control box door.
Developer Temperature Control
The developer is heated by a single 500 watt heating element located under the developer
tank in a heater exchange assembly.
Developer temperature is controlled by an IC temperature sensor mounted on the bottom
of the developer tank. This sensor is a constant current generator who’s output is directly
proportional to the temperature of the tank.
The temperature control is a proportional controller that allows full power to be sent to
the heating element during warm-up, when the processor is first turned ON. This will
be indicated by the DEV TEMP light on the control panel or LED L-2 on the logic
board being ON.
When the temperature in the tank is within 2 degrees f (1.1 C.) of the desired temperature,
the controller will start cycling the power to the heater to prevent temperature over run.
At this point the LEDs’ mentioned above will blink, indicating that the temperature is
very near its set point.
The temperature controller signals the triac switch Q2 through opto-isolator U-2 on the
AC interface board. The triac switches line voltage to the heater.
The desired temperature set point is adjusted with trim pot R-20 on the logic board.
NOTE: Clockwise rotation increases temperature. See Calibration Procedure below.
In the unlikely event of an electronic failure, providing continuous full power to the
heating element, an overtemp safety thermostat located on the heater exchange assembly
will open, thus disabling heat. In addition, a protective internal fusible link is present in
the heating element as an added safety feature. When an open heating element is found,
the operation of the triac should also be checked. (The heating element has a nominal
resistance value of approximately 25 ohms).
Note that the temperature controller is disabled if a low level condition exists in the
developer tank.
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