If The Green Leds Of The A8 Are Not All On - Agilent Technologies 8753ES Option 011 Service Manual

If the Green LEDs of the A8 Are Not All ON

The green LEDs along the top edge of the A8 post regulator are normally on.
Flashing LEDs on A8 indicate that the shutdown circuitry on the A8 post regulator is
protecting power supplies from overcurrent conditions by repeatedly shutting them down.
This may be caused by supply loading on A8 or on any other assembly in the analyzer.
Remove A8, Maintain A15W1 Cable Connection
1. Switch off the analyzer.
2. Remove A8 from its motherboard connector, but keep the A15W1 cable connected to A8.
3. Remove the display power cable.
4. Short A8TP2 (AGND) (see
5. Switch on the analyzer and observe the green LEDs on A8.
• If any green LEDs other than +5 VD are still off or flashing, continue to
A8 Fuses and Voltages" on page
• If all LEDs are now on steadily except for the +5 VD LED, the A15 preregulator and
A8 post regulator are working properly and the trouble is excessive loading
somewhere after the motherboard connections at A8. Continue to
Assemblies" on page
Check the A8 Fuses and Voltages
Check the fuses along the top edge of A8. If any A8 fuse has burned out, replace it. If it
burns out again when power is applied to the analyzer, A8 or A15 is faulty. Determine
which assembly has failed as follows.
1. Remove the A15W1 cable at A8. (See
2. Measure the voltages at A15W1P1 (see
having a small probe.
3. Compare the measured voltages with those in
• If the voltages are within tolerance, replace A8.
• If the voltages are not within tolerance, replace A15.
If the green LEDs are now on, the A15 preregulator and A8 post regulator are working
properly and the trouble is excessive loading somewhere after the motherboard
connections at A8. Continue to
Chapter 5
Figure 5-3 on page
5-13.
5-14.
Figure 5-5 on page
Figure 5-6 on page
"Remove the Assemblies,"
Power Supply Troubleshooting
If the Green LEDs of the A8 Are Not All ON
5-6) to chassis ground with a clip lead.
5-9.)
5-11) with a voltmeter
Table 5-2 on page 5-10.
next.
"Check the
"Remove the
5-13