Service manual

128 5
Power Supply Troubleshooting
FIND OUT WHY THE A1 +5 VD LED IS NOT ON STEADILY
FIND OUT WHY THE A1 +5 VD LED IS NOT ON
STEADILY
If the +5 VD LED is not on steadily, the +5 VD line voltage is missing or is not enough to
power the analyzer. The problem may be in the A50 DC-DC Converter, the A1 CPU, and
any of assemblies obtaining the power from +5 VD supply.
1. Check the A50 DC-DC Converter
1. Turn the analyzer power off. Disconnect the cable from A50P3. Turn the analyzer
power on.
2. Look at the A50 +5 VD LED. The LED is normally on.
3. Check that the voltage between the TP5 and GND is within +4.8 V to +5.4 V using a
voltmeter with a small probe.
• If the voltmeter reading is not within these limits, replace the A50 DC-DC
Converter.
• If the voltmeter reading is within these limits, the A50 +5 VD power supply is
verified. Then continue with the Measure the A1 +5V Voltage.
2. Measure the A1 +5VD Voltage
1. Reconnect the cable to A50P3. Turn the analyzer power on.
2. Check that the voltage between the TP4 (+5 V) and GND on A1 CPU is within +4.6 V
to +5.4 V using a voltmeter with a small probe. The TP4 location on A1 CPU is shown
in
Figure 5-3.
• If the voltmeter reading is not within these limits, inspect fuses on A1. The fuses on
A1 CPU is shown in
Figure 5-3.
• If the fuses are verified but the voltmeter reading is still not within these limits,
continue with the Disconnect Cables on the A1 CPU.
3. Disconnect Cables on the A1 CPU
1. Turn the analyzer power off.
2. Disconnect cables from the A1 CPU's connectors, J10, J11, J12, J13, J14, J16, J17, J18,
and J19. Don’t disconnect the J15. The connector locations are shown in
Figure 5-8.