Cv/Cc Status Annunciators Troubleshooting; Bias And Rail Voltages; Transformer Input - Agilent Technologies 6631B Service Manual

3 - Troubleshooting
E220 Front Panel comm UART input overrun
E221 Front Panel comm UART framing error
E222 Front Panel comm UART parity error
E223 Front Panel firmware input buffer overrun

CV/CC Status Annunciators Troubleshooting

The CV/CC annunciators are particularly helpful when troubleshooting a unit with no output voltage or
current. If the unit has passed self test the programming DAC circuits on the A2 circuit board are probably
working properly. If one of the annunciators is on then the problem is in either the CV or CC control
circuits located on the Main board A1. If UNR is indicated then neither the voltage nor the current circuits
are in control and the problem would be in the driver or output regulator stages circuits, also on A1 but after
the gating diodes, or the main power transformer.

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 3-3 lists the bias and rail 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 (R473-3) with the output on and no load on the supply.
Bias
+Rail (Agilent 6631B)
-Rail (Agilent 6631B)
+5 V secondary
+15 V secondary
-15 V secondary
+5 V Interface
+5 V Interface (Unreg)
1
Measured with respect to - Output at nominal ac input line voltage
2
Measured with reference to secondary common (R473 current sampling resistor, front)
3
Measured with reference to Interface Ground (EC306 black wire)
30
Table 3-3. Bias and Reference Voltages
Test Point Measurement
(See Figure 6-1)
1
A1 Main Heat Sink +20 V 10% (0.5V P/P)
1
A1 Q311 collector -8.5 V 10% (0.4V P/P)
2
A1 R473 +5 V 4%
2
A1 +C324 +15 V 5%
2
A1 D307 anode -15 V 5%
3
EA306 (red wire) +5 V 3%
3
EB306 (white wire) +5 V 3%
A3 Front Panel/Display Bd
A3 Front Panel/Display Bd
A3 Front Panel/Display Bd
A3 Front Panel/Display Bd

Transformer Input

18 Vac J302 pins 4-5 & 5-7
7.9 Vac J302 pins 3-5 & 5-9
20 Vac J305 pins 1-2 & 2-3
"
"
11 Vac J303 pins 1-3
"