Remove As, Maintain A15Wl Cable Connection; Check The A8 Fuses And Voltages - HP 8753E 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 A15Wl Cable Connection
1. Switch off the analyzer.
2. Remove A8 from its motherboard connector, but keep the A15Wl cable
connected to A8.
3. Short A8TP2 (AGND) (see F'igure 5-3) to chassis ground with a clip lead.
4. 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
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"Check the A8 Fuses and Voltages".

If all LEDs are now on steadily except for the +5 VD LED, the Al5
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preregulator and A8 post regulator are working properly and the trouble
is excessive loading somewhere after the motherboard connections at A8.
Continue to "Remove the Assemblies".
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
1. Remove the A15Wl cable at AS. (See Figure 5-5.)
2. Measure the voltages at A15WlPl (see F'igure 5-6) with a voltmeter having a
small probe.
Compare the measured voltages with those in Table 5-2.
3.
If the voltages are not within tolerance, replace A15.
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5-14 Power Supply Troubleshooting