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Remote Display Options 24683B, C & D Hydrastep 2468CB & 2468CD Manual
4-14 24685034
Indication Fault Analysis and Corrective Action
Bottom half of fault
LED illuminated and
odd LEDs flashing at
1Hz, or odd LEDs off.
Power present, but
loss of serial data.
Check that the wiring to connector PL1 in the remote
display unit is correct.
If wiring is correct, proceed as follows:
1. If a termination resistor is fitted, disconnect this from
the end of the daisy chain.
2. With an ac voltmeter, check the ac voltage between
pins 1and 5, and pins 2 and 5, on PL1.
3. An ac voltage is less than 1V indicates a fault on the
signal transmission lines. Check back to the previous
remote display in the daisy chain or to the 2468
electronics unit, as appropriate. If the correct ac
voltages are present at this location then a line break
is indicated.
4. If the ac voltages are still low then either the lines are
short-circuited or there is a board fault. Disconnect the
remote displays upstream and re-check the ac
voltages. If there is a voltage of less than 1Vac at the
2468 electronics unit (with PL3 removed) then the
display board is faulty. Remove this board and fit a
serviceable item.
Bottom half of fault
LED illuminated and
even LEDs flashing at
1Hz, or even LEDs off.
Power present, but
loss of serial data.
Check that the wiring to connector PL2 in the remote
display unit is correct.
If wiring is correct, proceed as follows:
1. If a termination resistor is fitted, disconnect this from
the end of the daisy chain.
2. With an ac voltmeter, check the ac voltage between
pins 1and 5, and pins 2 and 5, on PL2.
3. An ac voltage is less than 1V indicates a fault on the
signal transmission lines. Check back to the previous
remote display in the daisy chain or to the 2468
electronics unit, as appropriate. If the correct ac
voltages are present at this location then a line break
is indicated.
4. If the ac voltages are still low then either the lines are
short-circuited or there is a board fault. Disconnect the
remote displays upstream and re-check the ac
voltages. If there is a voltage of less than 1Vac at the
2468 electronics unit (with PL7 removed) then the
display board is faulty. Remove this board and fit a
serviceable item.
Table 4.1 (cont.) - Fault Analysis and Correction Chart