Hitachi C28W40TN, Service Manual

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5
POWER AND DEFLECTION ADJUSTMENT
+B VOLTAGE ADJUSTMENT
•
AC input voltage = 230V ± 5V/50Hz
•
Turn +B voltage (R982) to mid-point (if pre-adjustment not done).
•
Receive Philips circuit pattern. Switch on chassis and set the brightness and contrast to maximum.
•
After applying heat run for 1 MIN. or more, turn R982 gradually and B (re-check after 30 secs)
Measuring point : +B voltage C958 + side
Gnd C958 - side
•
Set the value of +B voltage to the value shown in the table below.
MODEL +B VOLTAGE (V)
All D8 151V ± 0.2V
All A8 148V ± 0.2V
Min Load Max Load
+8V = 8V
±
5%
0.3A 0.8A
+5V = 5V
±
5%
0.3A 0.8A
+16V = 16V ,+3V – 0.5V 0A 1.6A
+16V(Phono) = +16V, (+ 3V, - 1V) 0A 200mA
+B 0.2A 0.8A
•
Check + B voltage in standby > 145V and < 160V.
Short circuit test (all rails). PSU should go into standby/reset/lockup (supply may have to be removed to restart). Audio rail should be
tested , Q921 source to 0V.
POWER AND DEFLECTION ADJUSTMENT
POWER GOOD LINE
•
Set picture to same conditions as above.
•
Measure pin 2 I903. Should be HI, if LOW then cut R962 (if fitted). If HI but no power down timing (see below)
then cut R955 (if fitted).
•
Check power down logic timing ( >40mS, < 300mS )
•
After setting power good , check operation at 200V AC mains
PRIMARY CURRENT LIMIT
(Pre-set R980 to mid point)
Rail Trip Load Check Load Trip Power Check Power
+B 1.2ADC 1.1A 180W 165W
+16V 2.24ADC 1.65A 36W 26W
+11V
(+5, +8)
1.60A 1.60A 18W 18W
TOTAL W 234W 209W
•
In standby apply full load +40%, to the +B & audio/+11V rails (dynamic load) as table above.
•
Adjust R980 until set trips out .
•
In standby apply check load. PSU should not trip.
STANDBY OPERATION CHECK
•
Check all rails (B and s5V) go to 0V.
•
Check +B does not rise above 160V