Tuttnauer EA - Page 35

2 SYSTEM IS ON - DISPLAY IS NOT LIT
e If the other LEDS are functioning the display is most likely damaged. Replace the
PREDG board.
3 SYSTEM ON, DISPLAY LIT, DIGITS ARE NOT VISIBLE
e Check for 5 V between TPland TP17
e If yes, calibrate POT 1 on PREDG board.
e If digits are still not visible, this may be due to a faulty display or a faulty micro
controller. Try to replace them or replace them or replace the complete PREDG
board .
4 SYSTEM ON, DISPLAY LIT, ERRONEOUS OR FRAGMENTED DIGITS
The reasons for that may be faulty Real Time Clock, displays or microcontroller.Replace
them or replace the complete PREDG board. |
5 SYSTEM ON, KEY RESPONDS WITHOUT BEEPING
The problem may be with the buzzer or the buzzer’s driver:
Replace the complete PREDG board, replace the buzzer or replace
transistor 2N2222A, Ol.
6 EXHAUST VALVE IS ALWAYS ON
The problem could be with the solenoid, the transistors, or the digital control, or a bad
connection..
e Check and properly connect or replace all connections to and from the
exhaust valve.
e The problem could be with Q4 or Q5 on the PREDG board. If after pressing
START and the water enters the chamber, the voltage on TP11 1s between
10V - 12V the control and the transistors are O.K. If not, replace the PREDG
board. At this point disconnect connector JP2 from the AJUNC3 board, and
check the valve’s control.
If the connection to the valve is OK, (please refer to the wiring diagram)
there must be a mechanical problem with the valve or the solenoid may be
damaged.
If the control is faulty, check and connect the flat cable between AJUNC3 and
PREDG, replace the cable if necessary. If this does not help, there may be a problem in
the LATCH DRIVE at U4 in PREDG. In that case the electronics unit should be
replaced.
7 EXHAUST VALVE IS ALWAYS OFF
e Check and connect or replace the connector between the EXHAUST
valve and the AJUNC3.
e Repeat transistors and control checks as in 7.6 but this time the voltage for
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