HP 5890 SERIES II Service Manual page 10

PART A NON- FUNCTIONING INSTRUMENT
A totally non- functioning or DEAD instrument is one that apparently isn' t working at all. It has no visual
indications (i.e., messages) on its front panel and produces no noise or heat.
The most obvious cause for such a problem is that line power is not reaching the instrument or that the
instrument is not turned on. First check that the Line Power Switch is ON. Then verify that the instru-
ment power cord is plugged into a proper receptacle. If neither of these acts restore the instrument to
operation, suspect that there may be a problem with the receptacle or the power being supplied to it.
This type of situation generally requires that a local electrical maintenance person be informed to reme-
dy the problem. However, on the rare occasion that power is being provided, but the instrument is not
working, the problem area must be isolated by tests and measurements on the instrument.
MEASUREMENTS AND/OR TESTS THAT NEED TO BE MADE ON ELECTRICALLY
ENERGIZED PORTIONS OF THE INSTRUMENT SHOULD BE PERFORMED ONLY BY
SERVICE- TRAINED PERSONNEL WHO ARE AWARE OF ALL INVOLVED HAZARDS.
Any one of several problems internal to the instrument can cause the non- functioning symptom. Since
the instrument operates under processor control, a faulty component in the CPU or Clock sections of
the Main Board may be the source of the problem. More commonly, a problem in the instrument' s pow-
er supply would be the most likely to cause this type of problem.
Two bits of information, plus the use of IPB, should enable service- trained personnel to isolate and
then correct the cause of the problem if it is power related. The first important bit of information is about
the fuses that are internal to the instrument. The second bit is the normal sequence of events that oc-
curs as the instrument is energized (Power On Sequence).
Fuse Information
Fuses have been installed at several locations within the instrument for the protection of major power
circuits. They are designed to open as quickly as possible to prevent damage to other components
within the circuit. Occasionally, an opened fuse may have been caused by a short onetime surge; how-
ever, it is far more common that a component within the protected circuit has failed. When an open fuse
is noticed, replace it once. If the replacement blows, suspect a component failure.
Fuses are located on the AC Power Board and on the Main Board. The AC Power Board fuses protect
the two high- power circuits. One fuse, (F1) or two in a split phase circuit (F3 & F4), protects the col-
umn oven heater and fan. Another fuse (F2) or two in a split phase circuit (F1 & F2) protects the main
power transformer. (Refer to Section 8 of the IPB portion of this document for power supply PCB infor-
mation. Refer to Section 9 of the IPB portion of this document for main PCB information.)
The three secondary voltages of the main power transformer are protected with fuses located on the
Main Board. F3 protects the 120 VAC secondary which ultimately provides heater power for all of the
zones. F4 and F5 protect the 40 VAC secondary which ultimately provides all of the DC supply voltages
(+5, +10, +15, - 15, +24, - 24). Fuses protect the 3 VAC secondary that is used for FID ignitor (F1)
and electronic flow sensor voltages (F2).
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