Emerson 2468CB, 2468CD manual 4-14, Bottom half of fault

Remote Display Options 24683B, C & D Hydrastep 2468CB & 2468CD Manual

Indication	Fault	Analysis and Corrective Action
Bottom half of fault	Power present, but	Check that the wiring to connector PL1 in the remote
LED illuminated and	loss of serial data.	display unit is correct.
odd LEDs flashing at		If wiring is correct, proceed as follows:
1Hz, or odd LEDs off.
		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	Power present, but	Check that the wiring to connector PL2 in the remote
LED illuminated and	loss of serial data.	display unit is correct.
even LEDs flashing at		If wiring is correct, proceed as follows:
1Hz, or even LEDs off.
		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

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