HP 5890 SERIES II Service Manual page 164

Oven Temperature Troubleshooting
Problem
1. Oven does not heat.
" WARN: OVEN SHUTOFF"
message appears on dis-
play.
2. Using the same sample
and conditions on this and
other chromatographs, the
retention times of this GC
differ.
3. Oven does not control.
4. Oven temperature runs
away.
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Probable Cause
a. Faulty fuse F4 or F5 on
main PCB.
b. Oven heater is open.
c. Faulty power supply PCB.
d. Faulty main PCB PCB.
a. Oven needs calibration.
a. Faulty main PCB.
a. Oven heater partially
grounded.
b. Faulty main PCB
SVC 5- 2
Corrective Action
1. Check both fuses.
2. If either fuse is bad, re-
place. If neither fuse is
bad, go to probable cause
b.
1. With instrument power off,
check resistance of oven
heater.
2. If it exhibits a dead or near
short, replace the oven
heater element.
3. If heater element is ok, re-
fer to probable cause c.
1. Replace power supply
PCB.
2. If problem persists, reinstall
original power supply PCB
and go to probable cause
d.
1. Check both fuses.
1. Calibrate oven per proce-
dure in this section..
1. Replace main PCB.
1. Ensure that the oven heat-
er is not coming in contact
with the oven shell or other
nearby components.
2. If problem persists, go to
probable cause b.
1. Replace main PCB.