Ceronix 1493 Service Manual page 81

Problem
1. Turn down M. Gain to minimum.
Retrace
Measure voltage, auto bias IC
Lines .
pins 2, 4, & 6 for 5.5V to 6.5V.
Also measure voltage, pins 3, 5,
& 7 for 1.1V to 2.7V
2. Measure voltage, LM324
pin 5. Should be less than 4.5V.
3. Check video gain line (J
scope sync on Vs
and verify V. & H. blanking.
Problem
1. If screen turns bright & shutdown.
Monitor
Shuts
2. If shutdown right after power up.
Down.
3. Disable fault; clip
Disable shutdown; clip V- to
4.
Problem
1.
With power applied, check voltage
No
ground to (V-) anode of diode
Power.
Measure voltage, V+ line is 0V &
2.
PS chirps
If fuse is blown.
3.
Ohm out 160V crowbar zener
4. If the power supply chirps and
high voltage can be heard.
5. If the power supply chirps, check
for shorted secondary voltages by;
Disconnect power to chassis.
Apply external DC PS to 16V
line at cathode of diode
Apply second DC voltage to 24V
line at cathode of
FBT Check at low voltage;
Tests
927
927
If old style C-Film (no solder
920
920 connection) & pin 5 voltage is 4.8V
add a 7.15K resistor pins 8 to 11.
Otherwise replace C-Film.
) If either V. or H. blanking is
215
215
, .2mS/cm, missing, go to that circuit for
215
331
further tests.
Tests
Check voltage across cap.
Check V+, Hfo, & EHT at power up.
to GND. If solution, check fault circuit.
019 019
.
Measure EHT,
109
109
Tests
If 0V to 100V, ohm out fuse
.
156 inrush current limiter
156
.
181
181
First, ohm out diodes;
If PS current less than .5A and 12V
line=11.5V to 12.5V, go to next test.
.
169
169
If PS current less than .3A, line OK.
Check base of H. output
.
168
168
drive waveform. If OK connect 24V
line to V+ line and check flyback
waveform at collector of
(Without H. deflection load, PS
chirps) If large and small pulses
observed, replace the FBT.
Probable Solution
If any of the voltages are
not in the listed voltage
range, replace IC
Probable Solution
should be less than 27KV.
Probable Solution
159 159
Ohm out crowbar zener diode
Also ohm out H. output Xsr
If the zener is shorted and the fuse
is blown, replace fuse
zener , power FET
181
181
and the C5184 IC
115
115
Ohm out the 17V line; V- to anode
of , , ,
141 139
141 141 141 149 149 139
J-Film pins 8-14 & IC
.
927 927
5-10V
846 846
146 &
146
25Ω to .5Ω.
.
181
181
.
433
433
146
,
146
,
136
136
.
, ,
132 132
pin 15.
115
115
, ,
142 168
142 168
, .
169 169 181 181
for
433
433
.
433
433
97