Main
Symptom
Unit
Display does not light when
the DIGITEL is turned on.
Unit is completely dead.
Display lit. Unit does not
respond to keyboard.
Display not lit. Power light
works. HV light flashes and
then lights continuously.
Unit goes into cool-down
mode early.
Display not lit. Power light
lit. Unit is inoperable.
Displayed current and
voltage readings are
incorrect.
Displayed pressure reading
is incorrect.
No high voltage output.
4-8
Service
Possible Cause
1. Power not connected to unit.
2. Check fuse on back panel and fuses on
power supply board.
3. Cover loose or removed.
4. Check Voltage Select switch setting.
1. Keyboard not plugged in properly.
2. Shorted key
1. Check ribbon cable from CPU board to
display board.
2. Display board.
3. CPU board.
1. Check pump select switch setting.
2. Shorted HV cable.
3. Defective ion pump.
4. Contaminated ion pump.
5. Excessive gas load.
1. Defective 5V supply. Check TP403
(Figure 4-5).
2. Display board.
3. CPU board.
1. Def 15V supply. Check TP401
(Figure 4-5).
2. Defective-15V supply. Check TP401
(Figure 4-5).
3. Check -5 .1 V reference adjustment. See
calibration procedure.
1. Check pump select switch.
2. Check torr/pascal setting.
1.
HV enable switch is in Off position.
2. Unit in standby mode.
3. Primary of HV transformer disconnected
from power supply board.
4. Power supply board.
5. HV board.
