Safety Related Adjustment - Sony TRINITRON Multiscan GDM-W900 Service Manual

GDM-W900
When replacing or repairing the shown below table, the
SECTION 3
SAFETY RELATED
following operational checks must be performed as a
safety precaution against X-rays emissions from the unit.
HV Regulator GB board [C4202
Circuit Check ¢ Mounted GB board
HV Hold-Down
Circuit Check
Beam Current
Protector#1
Circuit Check
Beam Current
Protector#2
Circuit Check
Voltage of 3rd
winding of FBT
Part Replaced ([4)
G board D4220
¢ Mounted G board
¢ Mounted GB board
G board D4204,D4206,D4220,
R4211,R4212,R4216,
R4219
¢ Mounted G board
ADJUSTMENT
a) HV Regulator Circuit Check
1) Confirm that the voltage of the pin @ of 1C4202
on GB board is within the voltage range shown be-
low.
Standard: 9.00+0.10 V DC
b) HV Hold-Down Circuit Check
1) Using an external DC power supply, apply the
voltage shown below between cathode of D4220 on
G board and ground, and confirm that the HV Hold-
Down circuit works. (TV Raster disappears) ,
+0.0
Check Condition: Less than 33.8 -0.1 V DC
GB board 1C4202 c) Beam Current Protector#1 Circuit Check
* Mounted GB board
G board R4222, R4223
¢ Mounted G board
¢ Mounted GB board
G board T4202(FBT)
¢ Mounted G board
Check Condition
Input voltage : 100~120 V AC
Input signal
Controls
B+ voltage
: 193~201 V DC
1) Record the initial regulation value of ABL-
SHUTDOWN and using a PC computer, input the
"255" for maximum value of resistor.
2) Connect to the Constant Current Jig (A) between pin
@ of T4202 (FBT) on G board and ground, and
confirm that the Beam Current Protector Circuit
works. (TV Raster disappears)
Check Condition: Less than 1.55 mA
: White dots or Cross Hatch d) Beam Current Protector#2 Circuit Check
: BRT and CONT — Minimum Input the initial regulation value of ABL-SHUTDOWN
that was recorded c)-1).
1) Shorted between pin @ of C4202 on GB board and
ground.
2) Connect to the Constant Current Jig (A) between pin
@® of T4202 (FBT) on G board and ground, and
confirm that the Beam Current Protector Circuit
works. (TV Raster disappears)
Check Condition: Less than 1.72 mA
e) Voltage of 3rd winding of FBT
—~20~-
1) Confirm that the voltage of the cathode of D4220 on
G board is within the voltage range shown below.
Satndard: More than 28.0 V DC |