HP 6259B Operating And Service Manual page 47

Table 5-7. Preregulator Troubleshooting (See Figure 4-4 for Waveforms)
STEP
ACTION
RESPONSE PROBABLE CAUSE
■
Connect oscilloscope between
TP85 (+) and TP103 (-).
a. Normal waveform.
b. Little or no voltage.
a. Proceed to step 2.
b. Defective 072, Q73, CR76, or C71.
Proceed to step 3.
2 Connect oscilloscope between
TP89 (+) and TP86 (-).
To avoid a
oscilloscope
a. Normal waveform
b. Little or no vottage.
a. Defective A2CR1, A2L1, T1, A2C1, A2C3.
b. Defective T70, CR88, R88, Proceed to
step 3.
fferential
j
remen t.
WARNING
otentially lethal shock hazard, a di
must be used in making this meast
3 Connect oscilloscope between
TP80 (+) and TP103 (-).
a. Amplitude incorrect.
b. Period incorrect.
a. Defective G71, C70, C72, CR74, CR75,
R75, R78, or R82.
b. CR78 defective. Proceed to step 4.
■
Connect oscilloscope between
TP82 (+) and TP103 (-).
Amplitude,dc reference,
or period incorrect.
Defective CR77, CR78, CR79, CR80,
CR82, CR84. Check R87.
5
Connect oscilloscope between
TP81 (+) and TP103 (-).
Amplitude, dc reference,
or period incorrect.
Defective CR81, CR83, R83, R86, C73.
Table 5-8. Checks and Adjustments Required After Semiconductor Replacement
REFERENCE FUNCTION OR CIRCUIT CHECK
ADJUST
Z1
Constant voltage and constant
current differential amplifiers.
Constant voltage (CV) line and load regu¬
lation. Zero volt output.
Constant current (CC) line and load regu¬
lation. Zero current output.
R110, or R113 (Option
020 or 040);
R117, or R119 (Option
021 or 040). See para.
5-81 thru 5-85 or 5-91
thru 5-95 as applicable).
Q1
Voltage clamp circuit.
CC load regulation
—
Q20
Short circuit protection.
Output current.
—
Q40, Q41
Mixer amplifier.
CV/CC load regulation. CV transient
response.
R47 (See para. 5-98),
Q42, A4Q101,
A4Q102
Driver and error amplifiers. CV/CC load regulation.
—
Q60, 061,
062, Q63
Reference regulator.
+12.4V, +6.2V, and —6.2V reference
voltages and reference circuit line regulation.
—
Q70 Overvoltage limit.
Limiting action and level.
—
5-13