If The Green Leds On 8 Are Not Ll On - HP 8753D Option 011 Service Manual

If the Green LEDs on 8 are not ll ON

The green LEDs along the top edge of the 8 post regulator are normally on.
Flashing LEDs on 8 indicate that the shutdown circuitry on the 8 post regulator is
protecting power supplies from overcurrent conditions by repeatedly shutting them down.
This may be caused by supply loading on 8 or on any other assembly in the analyzer.
Remove A8, Maintain A15W1 able onnection
1. Switch o the analyzer.
2. Remove 8 from its motherboard connector, but keep the 15W1 cable connected to 8.
3. Remove the display power cable W14. See Figure 5-5.
4. Short 8TP2 ( GND) (see Figure 5-3) to chassis ground with a clip lead.
5. Switch on the analyzer and observe the green LEDs on 8.
If any green LEDs other than +5VD are still o or ashing, continue to \Check the 8
Fuses and Voltages."
If all LEDs are now on steadily except for the +5VD LED, the 15 preregulator and 8
post regulator are working properly and the trouble is excessive loading somewhere after
the motherboard connections at 8. Continue to \Remove the ssemblies."
heck the A8 Fuses and Voltages
Check the fuses along the top edge of 8. If any 8 fuse has burned out, replace it. If it
burns out again when power is applied to the analyzer, 8 or 15 is faulty. Determine which
assembly has failed as follows:
1. Remove the 15W1 cable at 8. See Figure 5-5.
2. Measure the voltages at 15W1P1 (see Figure 5-6) with a voltmeter having a small probe.
3. Compare the measured voltages with those in Table 5-2.
If the voltages are within tolerance, replace 8.
If the voltages are not within tolerance, replace 15.
4. If the green LEDs are now on, the 15 preregulator and 8 post regulator are working
properly and the trouble is excessive loading somewhere after the motherboard connections
at 8. Continue to \Remove the ssemblies."
Remove the Assemblies
1. Switch o the analyzer.
2. Install 8. Remove the jumper from 8TP2 ( GND) to chassis ground.
3. Remove or disconnect all the assemblies listed below. See Figure 5-5. lways switch o
the analyzer before removing or disconnecting an assembly.
10 digital IF
11 phase lock
12 reference
13 fractional-N analog
RAFT
3/21/106 15:12
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Power Supply Troubleshooting 5-11