Hitachi 35UX85B/CZ68 Service Manual page 5

A6LXU
TECHNICAL CAUTIONS
High voltage limiter circuit operation check.
Adjustment Preparation
1. Connect a high voltage voltmeter between CPT anode terminal (anode capside) and the ground.
2. Set AC Input voltage to 120+3V.
3. Receive Circle Pattern or broadcast signal and set "BRIGHTNESS" and "CONTRAST" to maximum. Adjust the Screen
VR so that Beam Current is I& 0. 1 mA. (The voltage of ABL terminal -C741- should be 12V or less.)
1
CPT Anode
High Voltage Voltmeter
(DC Voltage Divider)
Use the voltmeter which can
indicate
up
to the first decimal
~ ,;r$ pedance; ,
-_-----.
k+
10 HV
9
+B
ABL
Less than i2V
CPT Ground Wire
I
I
Digital Voltmeter
Adjustment Procedure
1. Check that the normal high voltage and +B voltage is as below.
CHASSIS
EHT le
+B El
30.O(KV) 1.60rnA 140.0(V) 37.0 (KV)
CZ68
fl KV M.l mA +0.3v +1.3 KV
Adjustment Preparation
4. Set AC input voltage to 120*3V. Then, connect the VR (1 OOK-B) and Rl(27K) to R927 and ground side as below.
Note: At that time the value of VR should be maximum
Use the voltmeter of input impedance IOM ohm or more with
indication to the 1 st decimal place.
CPT Anode
/
CPT
High VoltageVoltmeter
I\
(DC Voltage Dwider)
+
+
-8
a-------
A -
Digital Vollmeter
c925
,I
R92.5
+
mm
R926
Adjustment Procedure
2. Keep CONTRAST, BRIGHTNESS, and SCREEN VR as in item (3). Reduce the VR value gradually, and check that the
picture disappears when high voltage is El. Immediately after checking that it disappears, turn off the set switch.
Remove the VR and high voltage voltmeter. When connecting or removing high voltage voltmeter to or from anode
cap, be sure to turn off the switch of the set. Also, be sure to perform it after the chassis discharge of residual high
voltage, because the high voltage of CPT anode may be left.
5