Agilent Technologies 6612B, Руководство по обслуживанию, Страница: 37 / 74

Troubleshooting - 3
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CV/CC Status Annunciators Troubleshooting
The CV/CC annunciators are particularly helpful when troubleshooting a unit with no output. If the unit has
no output voltage or current and one of the annunciators is on then the problem is in the control circuit
associated with that annunciator. An example of how this might be useful would be in a case where the
voltage and current are programmed to some positive value, there is no output voltage and the CV
annunciator is on. This indicates that the problem is probably in the Voltage Amplifier circuit. If the CC
annunciator were on then the problem would likely be in the Current Amplifier. If UNR is indicated then
neither the voltage nor the current circuits are in control and the problem would be in circuits after the
gating diodes such as the driver or output regulator stages.
When troubleshooting the CV/CC status annunciators or the status readback circuits, first measure the
voltage drop across the gating diodes; A1 D317 (CV) and D321 (CC). A conducting diode indicates an
active (ON) control circuit. This forward drop is applied to the input of the associated status comparator
(U328C and D respectively) and drives the output (CV_DETECT* or CC_DETECT*) low. The low signal
indicates an active status which is sent to the A2 board microprocessor. The front panel CV annunciator
indicates when the CV mode is active (CV_DETECT* is low). The front panel CC annunciator indicates
when the CC mode is active (CC_DETECT* is low). The UNREGULATED (UNR) annunciator comes
on when neither the CV nor CC is active.
Bias and Reference Supplies
Before troubleshooting any circuit check the bias and/or reference voltages to make sure that they are not
the cause. Table 3-3 lists the bias and reference voltage test points for the A1 Main Control , A2 Interface,
and the A3 Front Panel/Display boards. Unless otherwise noted, all voltages are measured with respect to
secondary common (R431) with no load on the supply.
Table 3-3. Bias and Reference Voltages
Bias Test Point Common Measurement
+5V primary A1 J206-1(Red) Chassis (J206-2 black) +5V +/- 0.15V
+5V secondary A1 R423 Secondary Common +5V +/- 0.2V
+15V secondary A1 R419 Secondary Common +15V +/- 0.6V
-15V secondary A1 R422 Secondary Common -15V +/- 0.6V
+15V secondary gated A1 F304 Secondary Common +14.2V +/- 5%
-15V secondary gated A1 F302 Secondary Common -14.2V +/- 5%
+Rail
1
A1 D311 cathode - Output +32V +/- 10% (100mV P/P)
-Rail
1
A1 D307 Anode Secondary Common -6.5V +/- 10% (100mV P/P)
+2.5V reference
2
A1 J307-6 Secondary Common +2.5V +/- 5%
1
Measured with respect to - Output at nominal ac input line voltage
2
the 2.5V reference originates on the A2 Interface board