Circuit Checks - Toshiba DW65X91 Service Manual

HIGH VOLTAGE CHECK
CAUTION: Checking should be done following the steps be-
low.
1. Connect an accurate high voltage meter. (See ANODE
VOLTAGE MEASURING METHOD)
2. Turn on the receiver. Set the BRIGHTNESS and CON-
TRAST to minimum (zero beam current).
3. High voltage must be measured below (B) kV.
Refer to table-1 for high voltage (B).
(See SETTING & ADJUSTING DATA on page 26)
4. Vary the BRIGHTNESS to both extremes to be sure the
high voltage does not exceed the limit under any condi-
tions.
CAUTION:
When the following parts fail, check the High Voltage after re-
placing.
Location
Name
No.
T461 Flyback Trans.
Z450 CR Block
C404 Capacitor
C407 Capacitor
C408 Capacitor
R465 Resistor
R466 VR
R467 Resistor
Q437 IC
ANODE VOLTAGE MEASURING METHOD
CAUTION: Take extra precaution when measuring this high
voltage. High voltages are also present in surround-
ing circuit boards (CRT DRIVE assembly, DEFLEC-
TION assembly, and POWER SUPPLY assembly).
1. Disconnect the FBT anode cable as outlined below. Meas-
ure high voltage at the point where the cable enters the
FBT.
2. Holding the rubber cover firmly, turn it counterclockwise
and check that the lock has been disengaged. (See Fig. b
on page 9.)
3. Determine the extent of the rubber cover before discon-
necting the cable.
4. Pull straight up the anode cable to disconnect.
5. When reconnecting the cable, proceed in the reverse or-
der.
After reconnecting, tug on the cable to check that it is se-
cure.

CIRCUIT CHECKS

Remark
TFB3083AD
TPA5007
1200pF, ±3%
1200pF, ±3%
1200pF, ±3%
2.2kΩ ±1%
2kΩB
5.6kΩ ±1%
TA75902p
– 25 –
FS CIRCUIT CHECK
The Fail Safe (FS) circuit check is indispensable for the final
check in servicing. Checking should be done following the
steps below.
1. Turn the receiver on.
2. Temporarily short TP-R-1 and TP-X-1 on the DEF Board
with a jumper wire.
Raster and sound will disappear.
3. The receiver must remain in this state even after removing
the jumper wire. This is the evidence that the FS circuit is
functioning properly.
4. To obtain a picture again, temporarily turn the receiver off
and allow the FS circuit more than 5 seconds to reset. Then
turn the receiver on to produce a normal picture.
Troubleshooting Guide for Fail Safe Circuit
(When Fail Safe Circuit Operate)
Check that the set returns to normal operation when
the terminal "TP-X1" is grounded with jumper wire.
YES
Check the voltage across
Capacitor C471 is
approximately (C) volts.
Refer to table –4 for
FBT detection voltage
(C) .
YES
(See SETTING & ADJUSTING
DATA on page 26)
Fail Safe circuit is faulted.
NO
Power circuit or
horizontal circuit
or vertical circuit
is faulted.
NO