Read Sony GDM-17E21 Service Manual online
GDM-17SE2T
– 14 –
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.
SECTION 3
SAFETY RELATED ADJUSTMENT
HV ADJ
Part Replaced ([)
RV401
Part Replaced (])
D board
IC401, IC403, RV401,
FBT(T404),
FBT(T404),
D425,
R423,
R460,
R461,
R462,
R493
• Mounted D board
D board
IC401, D439,
D442,
D443,
D444,
R422,
R435,
R448,
R490
• Mounted D board
D board
IC401, D429,
D445,
R435,
R470,
R472,
R487,
R497,
R501,
R503,
R508
• Mounted D board
HV Regulator
Circuit
Circuit
HV Hold-Down
Circuit
Circuit
Beam Current
Protector Circuit
Protector Circuit
*
Confirm one minute later turning on the power.
Check Condition
• Input voltage : 118–122 V AC
• Input signal
: White dots or Cross Hatch
• Controls
: BRT and CONT
→
Minimum
a) HV Hold-Down Check
1) Using an external DC Power supply, apply the volt-
age shown below between cathode of D439 on D
board and GND, and confirm that the HV Hold-
Down circuit works. (TV Raster disappears)
Standard voltage : Less than 28.40 V DC
b) Beam Current Protector Circuit Check-1
(Hardware logic)
1) Record the initial value of ABL-SHUTDOWN and
using a PC computer, input the “255” for resistor
value.
2) Connect a resistor (100 K
Ω
) between pin
2
of
CN811 and pin
!,
of CN812.
3) Confirm that the raster appears on the CRT screen.
4) Connect a variable resistor (12 K
Ω
or more) and
an ammeter in serles between pin
!]
of FBT (T404)
and GND, then, decrease gradually the resistance of
the variable resistor from mamximum to minimum,
and confirm that the Beam Current Protector Circuit
works (TV Raster disappears).
The current must be within the range shown below.
Standard current: Less than 1.48 mA
5) Turn off the Unit.
c) Beam Current Protector Circuit Check-2
(Software logic)
1) Make a short between pin
!-
of CN811 and pin
1
of
CN810.
2) Confirm that the raster appears on the CRT screen.
3) Connect a variable resistor (12 K
Ω
or more) and an
ammeter in serles between pin
!]
of FBT (T404) and
GND, then, decrease gradually the resistance of the
variable resistor from maximum to minimum, and
confirm that the Beam Current Protector Circuit
works (TV Raster disappears).
The current must be within the range shown below.
Standard current: Less than 1.30 mA
4) Back the value of ABL-SHUTDOWN to the initial
regulation value.
5) Turn off the Unit.
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