Safety Related Adjustment - Sony HMD-A400 Service Manual

When replacing parts shown in the table below, the
following operational checks must be performed as a
safety precaution against X-ray emissions from the unit.
HV Regulator
D board
Circuit
HV HOLD D board
DOWN Circuit
Beam Current
D board
Protector Circuit
Allow the unit to warm up for one minute prior to checking
the following conditions:
a) HV Regulator Check
1) Input white cross hatch signal. (fH = 69 kHz)
2) CONT maximum and BRT center
3) Cut off Screen VR (G2).
4) Input voltage: 120 ± 2 VAC
5) Confirm that the voltage is within the voltage range
shown below.
Standard voltage: 26.9 KV ± 0.4 KV
When replacing components identified by ], make sure
6)
to recheck the High Voltage.
7) Verify the High Voltage as shown above (26.9 KV ± 0.4
KV) is within specification. If not, set H. SIZE data at
minimum (-127) and then adjust RV501 on "D" Board.
SECTION 3

SAFETY RELATED ADJUSTMENT

Part Replaced ( ] )
IC502, R515, T501 (FBT)
• Mounted D Board
D538, IC901, Q534, R521,
R551, R552, R598, R599,
T501 (FBT)
• Mounted D Board
IC901, R911, R949, R950,
T501 (FBT)
• Mounted D Board
RV501
8) After adjusting the High Voltage within specification,
put the RV cover on RV501 as shown below and apply
sufficient amount of RTV around RV501.
b) HV Protector Circuit Check
1) Confirm that the voltage between cathode of D517 an
GND is more than 27.5 VDC.
2) Using an external DC Power supply, apply the voltage
shown below between cathode of D517 on "D" and
GND, and confirm that the HV Hold-Down circuit
works. (Raster disappears) Apply DC Voltage: Less than
35.8 VDC.
Check Condition
• Input voltage
• Input signal
• Controls
• B+ Voltage
c) Beam Protector Check (Software logic)
1) Using an external current source, apply < 1.55mA
between pin qa of FBT (T501) and GND, and confirm
that the raster fades out.
Check Condition
• Input voltage
• Input signal
• Controls
d) B+ Voltage Check
1) Input white cross hatch (fH = 69 kHz) signal.
2) CONT (max) & BRT (center)
3) Input voltage: 120 ± 2 VAC
Note: Use NF power supply or make sure that distortion
factor is 3% or less.
4) Confirm that the voltage is within the voltage range
shown below.
Standard voltage: 179 ± 3.0 VDC
3-1
HMD-A400
: 120 ± 2 VAC
: (fH = 69 kHz), White Cross Hatch
: CONT (max) & BRT (center)
: 179 ± 3.0 VDC
: 120 ± 2 VAC
: (fH = 69 kHz), White Cross Hatch
: CONT (max) & BRT (center)