3 - Troubleshooting
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 D328 (CV) and D325 (CC). A conducting diode indicates an active (ON) control circuit. This forward drop is applied to the input of the associated status comparator (U306A 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 Rail Voltages
Before troubleshooting any circuit check the bias and/or rail voltages to make sure that they are not the cause. Table
Table 3-3. Bias and Reference Voltages
Bias | Test Point | Common | Measurement | |
| (See Figure |
|
|
|
+Rail1 (Agilent | A1 TP 310 | - Output | +38V | 10% (800mV P/P) |
6632B/66332B) |
|
|
|
|
+Rail1 (Agilent 6633B) | A1 TP 310 | - Output | +73V | 10% (2.5V P/P) |
+Rail1 (Agilent 6634B) | A1 TP 310 | - Output | +130V 10% (2.2V P/P) | |
A1 TP 311 | - Output | |||
6632B/66332B) |
|
|
|
|
A1 TP 311 | - Output | |||
A1 TP 311 | - Output | |||
+5V secondary | A1 R317 | Secondary Common | +5V 4% | |
+12V secondary | A1 D470 cathode | Secondary Common | +12V | 5% |
+15V secondary | A1 R318 | Secondary Common | +15V | 4% |
A1 D471 anode | Secondary Common | |||
A1 R315 | Secondary Common | |||
V_Ref | A1 R475 | Secondary Common | +2.5V 6% | |
+5V Interface2 | E306 (red wire) | E 306 (black wire) | +5V 3% | |
1Measured with respect to - Output at nominal ac input line voltage
2Measured with reference to Interface Ground (E306 black wire)
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