Fault in Specific Station only | TOA Electronics TOAEXES-5OOO

8-3. FAULT IN SPECIFIC STATION ONLY

Find the cause according to the following table if the fault

lies with a specific station only, not with all stations.

	CHECK-ITEM	CAUSE
Dialing can not	LMU Lamp is	Disconnection of both T & R-Lines.
be made at privacy	off.	Guard resistor 330 on LMU is
off mode.		burned out due to T & R-Lines
		short.

Specific key does not operate.

Calling tone can not be heard.

Dialing tone can not be heard on dialing.

other party can not be heard.

Sound is not trans-

mitted to the other party.

On dialing, noise is heard by the called party.

Specific Lamp			T & R-Lines are shorted.
on	LMU is
brighter		than
normal.
LMU Lamp		is	Fault in the station.
on in normal.			(Replace PCB board.)
Replace the			Fault in key board switch or
station		and	matrix circuitry.
make sure that			Fault in the dial generator.
the station			(Replace PCB board.)
is not faulty.
Same sympton			Short or open in R-Line.
remains even			Fault in the demodulation cir-
if the station			cuitry on LMU.
is replaced.			(Check LM-380, MT-547.)
Becomes normal			Disconnection of R-Line or im-
if	the station		proper connection of the station
is replaced.			connector.
			Fault in MT-547 on LMU.
			Station fault.
Same sympton			Short or open in T-Line.
remains		even	Fault in the modulation cir-
the station			cuitry on LMU.
is replaced.
Becomes normal			Fault in MIC circuitry of the
if	the station		station. (Replace MIC or PCB)
is replaced.
Same sympton			One of T-Lines is disconnected.
remains		even
the	station is
replaced.
Becomes normal			Fault in MIC element.
if	the station		Fault in T-Line of the station.
is	replaced.		Low frequency oscillation of
			MIC AMP. (Faulty bypass capaci-
			tor)

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