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Service Manual
Third edition, June 1997
4.1 The Motherboard of the I/O Box
The motherboard in the I/O Box contains a power supply, a
communication watch dog with System Failure output,
seven relay outputs and seven slots for plug in of various
Interface Boards. The seven serial channels are directly wired
to the seven connectors for the Interface Boards.
4.1.1 Watch Dog LED
There is a red LED (H4) on the motherboard indicating that
there has been an interruption of the communication with
the Work Station. The LED remains lit after the watch dog
has been triggered. This LED will normally be lit since this
watch dog will trigger while the Work Station is starting up
after a black-out or after the Work Station has been switched
on. When there is an interruption of the communication to
the Work Station, watch dog is triggered and the watch dog
LED lights up and remains lit.
Check function of I/O Box by following the steps below.
1. Open cover of I/O Box.
2. Locate the red watch dog LED and a reset switch right
next to it on the motherboard of the I/O Box.
3. Beside it there is a reset switch.
4. Make sure the Work Station (if more than one Work
Station – the master Work Station) is running.
5. Press the reset switch in the I/O Box.
6. Wait for approximately half a minute. The watch dog
LED should not light up.
X30 X31 X8 X37
H3
H2
H4
H10
RST
X1
H11
X2
H12
X3
H13
X4
H14
X5
H15
X6
H16
X7
H17
Voltage
selector
F3 F4
X10 X11 X12 X13 X14 X15 X16 X17
X9
Figure 4-3 shows the motherboard of the I/O Box.