Overall Troubleshooting - HP 6269B Operator’s, Organizational, Direct Support And General Support Maintenance Manua L

TM 11-6625-2958-14&P
5-56 OVERALL TROUBLESHOOTING PROCEDURE
5-57 To locate the cause of trouble, follow Steps
1, 2, and 3 in sequence:
(1) Check for obvious troubles such as trip-
ped circuit breaker, defective power cord, incor-
rectly strapped rear terminals, input power failure
or defective meter. Next, remove the top and bot-
tom covers and inspect for open connections,
charred components, etc. , paying particular atten-
tion to both sides of the main circuit board.
to Paragraph 5-64 for the main circuit board remov-
METER
STEP
COMMON
1
+S
2 +S
3 +S
4
+S
5
+S
6
+S
SYMPTOM
Low or no output voltage
(Overvoltage lamp may be on or off)
High output voltage
High ripple
Table 5-2. Reference and Bias Voltages
(Refer to Schematic and Figure 7-10 for test point locations)
METER
NORMAL
POSITIVE
VDC
TP63 +12.4 ± 7%
TP64 +6.2 ±5%
TP65 -6.2 ± 5 %
TP66
+11 ±15%
TP67 -4.0
± 1 2 . 5 %
TP68 -2.4±12.5%
Table 5-3.
a.
b. Crowbar not reset or defective. Refer to Table 5-4.
c.
Refer to Table 5-4.
a.
b. Open circuit between sensing terminals (*S) and output ter-
c.
a.
b. Incorrect reference and\or bias voltages. Refer to Table
c.
al procedure. ) If the trouble source cannot be de-
tected by visual inspection, re-install the main
circuit board and proceed to Step (2).
(2) In almost all cases, the trouble can be
caused by incorrect dc bias or reference voltages;
thus, it is a good practice to check the voltages
in Table 5-2 before proceeding with Step (3). Re-
fer to Figure 7-10 for the location of the test points
listed in Table 5-2.
(3) Disconnect load and examine Table 5-3
(Refer
to determine your symptom and its probable cause.
NORMAL
RIPPLE (P-P)
2.0mV
0.5mV
2.0mV
2.0V
0.8V
0.4V
Overall Trouble shooting
PROBABLE CAUSE
Front panel meter defective.
Series regulator or preregulator feedback loop defective.
Front panel meter defective.
minals (*OUT). Refer to Table 5-4.
Series regulator or preregulator loop defective. If crowbar
does not trip, it also is faulty. Refer to Table 5-4.
Ground loops in operating setup. Refer to Paragraph 5-15.
5-2.
Supply crossing over to constant current operation under
loaded conditions.
Check current limit setting or constant
5-10
PROBABLE CAUSE
CR61, CR62, Q60, Q61, Q62,
Q63
VR60, VR61, Q62, Q63
VR60, VR61, Q62, Q63
C44, CR53, CR54
C44, CR53, CR54, CR45, CR46,
CR47, CR48, CR49
CR54, CR45, CR46, CR47,
CR48, CR49
.