Sony GDM-F500T9 service manual Section Safety Related Adjustment, + Voltage Check

GDM-F500/F500T9

SECTION 3

SAFETY RELATED ADJUSTMENT

When replacing or repairing the shown below table, the

following operational checks must be performed as a

safety precaution against X-rays emissions from the unit.

	Part Replaced (])
HV Regulator	G Board	IC901,	T901
Circuit Check		∙ Mounted G board
HV Protector	G Board	Q907,	Q908,	D913,
Circuit Check		D916,	C923,	R920,
		R927,	R952,	T901
		∙ Mounted G board
Beam Current	D Board	R011,	R1068
Protector Circuit		∙ Mounted D board
Check	G Board	IC901,	IC902,	Q907,
		Q908,	D902,	D918,
		D919,	R923,	R928,
		R933,	R934,	R942,
		R944,	R945,	R947,
		R948,	R951,	R952,
		T901
		∙ Mounted G board

*Confirm one minute later turning on the power.

a)B+ Voltage Check

Check Condition

∙Input voltage : 100 ~ 240 VAC

∙ Input signal : White Cross Hatch at 120.7 kHz

∙Beam control : BRT and CONT → MAX

∙ Standard : 200 ± 3.0 V DC

b)HV Regulator Circuit Check

1)Confirm that the voltage of the + side of C910 on G board is within the voltage range shown below. Standard: 8.940 ~ 9.065 V DC

c)HV Protector Circuit Check

1)Confirm that the voltage between cathode of D913 on G board and GND is more than 26.5 V DC.

2)Confirm that the HV protector circuit works and TV Raster disappears when apply the voltage as shown below between cathode of D913 and GND using an external DC power supply.

Check Condition

∙Input voltage : 100 ~ 240 VAC

∙ Input signal : White Cross Hatch at 120.7 kHz

∙Beam control : BRT and CONT → MIN

∙ Standard : Less than 34.20 V DC

d)Beam Current Protector Circuit Check-1

(Hardware)

Connect a variable resistor (20 kΩ or more) and an am- meter in series between pin !Á of T901 (FBT) and –15 V line. Decrease gradually the resistance of the vari- able resistor from maximum to minimum, and confirm that the Beam Current Protector Circuit works and TV Raster disappears. The current must be within the

range shown below. Check Condition

∙ Input signal : White Cross Hatch at 120.7 kHz

∙Beam control : BRT = 0, CONT = 0

∙ Standard : 1.49 mA

e)Beam Current Protector Circuit Check-2 (Software)

1)Short between + of C937 and GND.

2)Connect a variable resistor (20 kΩ or more) and an ammeter in series between pin !Á of T901 (FBT) and –15 V line. Decrease gradually the resistance of the variable resistor from maximum to minimum, and confirm that the Beam Current Protector Circuit

works and TV Raster disappears. The current must be within the range shown below.

Check Condition

∙ Input signal : White Cross Hatch at 120.7 kHz

∙Beam control : BRT = 0, CONT = 0

∙ Standard : 1.59 mA

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