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27 .01.1998 / Page 10
Doc. No: 4812 714 12124
Display
The display is of the vacuum fluorescent type. It is driven directly from the microprocessor high voltage
outputs. These are provided with internal pull down resistors. The display has a matrix of segments and grids.
The grids are continuously scanned by the processor, except for a pause during key scanning. Each grid is held
high for a moment, then there is a short blanking period before the next grid is activated. The segments are
pulled high when they should be lit during scanning.
Buzzer with ping
By controlling the supply voltage to the Buzzer the volume can be controlled. This is used to form the clock-like
PING function. Transistor 7152 feeds the buzzer with the voltage over the capacitor 2152. The resistor 3152
discharges the capacitor logarithmically. This gives the clock like decay effect. The transistor 7153 loads the
capacitor again at request from the micro processor.
The buzzer (4625) voltage is switched by transistor 7251. The base of 7251 is fed with a 2048 Hz square wave
from the micro processor.
Convection Temperature Sensor Interface (Crisp Convection and Fuzzy Crisp Convection only)
This interface works in the same way as the fuzzy temperature sensor interface.
Error Codes
Certain fault conditions are indicated by an error code. The following codes are implemented:
ERR 0
Convection temperature sensor fault Not connected or short circuit
ERR 1
Short circuit in the MW relay
ERR 6
Weight sensor calibration has not been performed
ERR 7
Humidity sensor is defect or has not been connected
ERR 8
Impossible to write to E PROMERR 9Options have not been set
ERR A No wheel detected on weight sensor
ERR B No pulses from the weight sensor or <4267 Hz
ERR C Fuzzy temperature sensor fault. Not 19-41 C˚
Test Mode
The microprocessor program contains a test mode, in order to simplify checking and trouble shooting of the
control system. To enter test mode: Keep the STOP button pressed, open S1 or open the door of the oven and
force a reset of the microprocessor. This can be done by short circuiting the base and emitter of 7202, or by
disconnecting the power at least two seconds.
To exit test mode press the STOP button.
Test Mode Entry
Action
Open the door
Release the TT-stop switch. This must be done only if the
power has been disconnected for more than 30 sec.
Press STOP and, at the same time, connect power
Close the door
When test mode is entered, all segments in the display will be lit. Close the door. The Running mask number
is output to the display pins for 500 milliseconds. Then the mask number and the option setting will be
indicated in the following format:
MT 263/WH
8538 263 53291
Whirlpool Europe
S E R V I C E
Customer Service
Reaction
All segments on the display are lit.
The display will darken for half a second while the
Running mask number is output to the display pins.
Mask number and Options will show on the display in
the format MMMOO (Ex: 1 02).
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