LG Electronics 120S Troubleshooting Examples, Input circuit troubles and corrective actions

Chapter 11 Troubleshooting

11.4 Troubleshooting Examples

Possible troubles with various circuits and their corrective actions are explained.

11.4.1 Input circuit troubles and corrective actions

The followings describe possible troubles with input circuits, as well as corrective actions.

Condition		Cause	Corrective Actions
	Leakage current of external device		y Connect an appropriate register and capacity,
	(Such as a drive by non-contact switch)
Input signal			which will make the voltage lower across the
doesn’t turn off.		AC input	terminals of the input module.
	C	Leakage current	AC input
	R
			C
		~
	External device		R
	Leakage current of external device		~
Input signal
	(Drive by a limit switch with neon lamp)		y CR values are determined by the leakage current
doesn’t turn off.
			value.
(Neon lamp
		AC input	− Recommended value C : 0.1 ~ 0.47 ㎌
	C	Leakage current
may be still on)			R: 47 ~ 120 Ω (1/2W)
	R
	External device	~	Or make up another independent display circuit.
Input signal	Leakage current due to line capacity of wiring cable.		y Locate the power supply on the external device
doesn’t turn off.			side as shown below.
		AC input	AC input
		Leakage current
	External device	~	~
			External device
Input signal	Leakage current of external device (Drive by switch with		y Connect an appropriate register, which will make
	LED indicator)
doesn’t turn off.			the voltage higher than the OFF voltage across the
		DC input	input module terminal and common terminal.
		Leakage current	DC input
	R
			R
	External device

Input signal	y Sneak current due to the use of two different power			y Use only one power supply.
	supplies.
doesn’t turn off.				y Connect a sneak current prevention diode.
		DC	input
		L		DC input
				E1
	E1	E2
				L
				E

yE1 > E2, sneaked.

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