Hitachi 27MMV30B Service Manual page 5

TECHNICAL CAUTIONS
HV Protection circuit operation checking.
Hiah voltaae limiter circuit operation check and over voltaae protection circuit operation check.
Adjustment Preparation
(1) Connect a high voltage voltmeter between CPT anode terminal (Anode cap side) and the ground as below.
(2) Set AC input voltage to 120&3V.
(3) Receive Hitachi circle pattern and set "Bright" and "CONTRAST" to max. Adjust Screen VR so that Beam
Current is 1 B 1 .15&O. 1 mA. (The voltage of ABL terminal-C725 both ends should be 12V or less)
CPT
\
High voltage
voltmeter
(DC voltage divider)
ital voltmeter
GND WIRE
Use the voltmeter
Of
input
impedencelOM ohm or more
with indication to the 1st
decimal place.
Adiustment Procedure
(1) Check that the normal High Voltage is 27.0+1.5KV and +B Voltage is 130+1.5V.
(2) Connect jig A to the Both end of R706 and check that the power is turned off.
D706
+56V 0-w To D718
4-s-J
jig=kR 1/8W
w
3
c725
Less than 12V
0.1150
(3) Disconnect the AC plug and remove jig A.