GDM-500PS/500PST/500PST9
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.
a) HV Regulator Circuit Check
1) Confirm that the voltage of the pin 2 of CN901 on
D board is within the voltage range shown below.
Standard: 9.00 ± 0.065 VDC
b) HV Protector Circuit Check
1) Confirm that the HV protector circuit works and TV
Raster disappears when apply the voltage as shown
below between pin 3 of CN901 on D board and
GND using an external DC power supply.
Check Condition: Less than 34.10 VDC
c) Beam Current Protector Circuit Check-1
1) Measure HV voltage and record that value.
2) Shorted between pin 1 and pin 4 of CN901 on D
board.
3) Connect to the Constant Current Jig (A) between pin
1 of CN901 on D board and GND, confirm that the
Beam Current Protector Circuit works and HV go
down more than 1.25 kV from the value of (1).
Check Condition: 1.50 mA
d) Beam Current Protector Circuit Check-2
1) Connect to the Constant Current Jig (B) between pin
1 of CN901 on D board and GND, confirm that the
Beam Current Protector Circuit works and TV Ras-
ter disappears.
Check Condition: 1.59 mA
e) Voltage of 3rd winding of FBT
1) Confirm that the voltage of pin 3 of CN901 on D
board is within the voltage range shown below.
Standard: more than 28.0 VDC
Check Condition
Input voltage : 100 ~ 240 VAC
Input signal : White Cross Hatch at 107 kHz
Beam control : BRT and CONT → Minimum
B+ voltage : 195 ~ 205 VDC
SECTION 3
SAFETY RELATED ADJUSTMENT
Part Replaced (])
D Board IC901, T902
• Mounted D board
D Board Q660, Q661, D916,
D935, C924, R665,
R667, R940, R980,
T902
• Mounted D board
G Board PH680, Q680, Q683,
D680, R680, R685,
R686, R687, R688,
R689
• Mounted G board
D Board IC901, D904, D907,
D908, R011, R908,
R909, R921, R925,
R926, R929, R930,
T902
• Mounted D board
HV Regulator
Circuit Check
HV Protector
Circuit Check
Beam Current
Protector Circuit
Check
3-1
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