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3 - Troubleshooting
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E221 Front Panel comm UART framing error A3 Front Panel/Display Bd
E222 Front Panel comm UART parity error A3 Front Panel/Display Bd
E223 Front Panel firmware input buffer overrun A3 Front Panel/Display Bd
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 either the CV or CC annunciators is on then the problem is in either the CV or CC
control circuits located on the A1 Main board. If UNR is indicated then neither the voltage nor the current
circuits are in control and the problem would be in the main power transformer or the driver or output
regulator stages circuits, also on A1 but after the gating diodes.
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 (R431-3) with no load on the supply. See Figure 6-1 for test point locations.
Table 3-3. Bias and Reference Voltages
Bias Test Point Measurement
+5V primary
1
A1 E320(Red wire) +5V +/- 0.15V
+5V primary (unreg)
1
A1 E3321(White wire) +5V
+5V secondary
2
A1 R423 (jumper) +5V +/- 0.2V
+15V secondary
2
A1 R419 (jumper) +15V +/- 0.6V
-15V secondary
2
A1 R422 (jumper) -15V +/- 0.6V
6611C +Rail
3
A1 Main Heat Sink +20V +/- 10% (50mV P/P)
6612C +Rail
3
A1 Main Heat Sink +32V +/- 10% (120mV P/P)
6613C +Rail
3
A1 Main Heat Sink +81V +/- 10% (300mV P/P)
6614C +Rail
3
A1 Main Heat Sink +130V +/- 10% (400mV P/P)
-Rail
3
A1 D307 Anode -6.8 to - 9.1V (100mV P/P)
1
Measured with respect to Primary common (Black wire at A1 E324).
2
Measured with respect to Secondary common (R431-3).
3
Measured with respect to - Output at nominal ac input line voltage.