HP 6177B Operating And Service Manual page 29

Table 5-2. Reference Voltages
(Refer to the Schematic for Test Point Locations)
I
MITER
TvrETER
NORMAL
NORMAL
I STE?
COMMON POSITIVE VDC
RIPPLE (P- PI
PROBABLE CAU SE
I A3 3 ll.8
I
ImV
VRI2. Oll-015
2
A3
4
- ?
o.~
lOOw.V
VRS
3
I
A3
I
5
5.9 I lOOw.V
VR5, adjustment of R3S
4
I
A3
6 5.6 I
5f.lV
VRI2
5 2 A3 16.2 2mV
I
VRS, 01, VRI
Table 5-3. Overall Troubleshooting
SYMPTOM
PROBABLE CAUSE
Poor Programming
a. Main feedback loop, Guard, or voltage limit circuit
Varying controls has little or no effect on defective. Proceed to Paragraph 5-45 fo:: further iso-
front panel meter reading. lation.
Actual Output Current
a. Main feedback loop, Guard, or voltage limit circuit
(according to external meter)
defective. Proceed to Paragraph 5-45 for further iso-
does not cOincide with front panel meter lation.
reading. (May be higher or lower. I
Inability to Zero Guard a. C23 defective.
b. R49 defective.
High Ripple
a. C29 or 020 leaky or defective.
b. High ripple in reference circuit. See Table 5-2.
c. Poor line regulation.
d. Poor load regulation.
Poor Line Regula tion a. Improper measurement technique. See Paragraph 5-15.
b. Check reference circuit.
See Table 5-2.
c. Check Cl, C2, C5, and C 13 for defect.
d. Check CR 1 and CR2 for defect.
,
Poor Load Regulation a. Improper measurement technique. See Paragra ph 5-13.
b. Check for shunt leakage paths external to the supply.
~
c. Check reference circuit.
See Table 5-2.
d. If poor load regulation eXists in lower current ranges
only. check bleed transistor Ol. for open and VRl for
short.
e. 03 shorted.
Unit Oscillates
a. C14, C20, C21, or C22 defective.
b. CI0, Cll, or C3S defective.
5-9