Supply Restarting Every 1.5 Seconds (Kick Start); Low Voltage Supplies - Agilent Technologies 8564EC Service Manual

Supply Restarting Every 1.5 Seconds (Kick Start)

See function blocks G, H and L of A6 power supply schematic diagram
in the component-level information binder.
If there is a short on the power supply or on one of the other assemblies,
the power supply will attempt to "kick start." (Every 1.5 seconds the
supply will attempt to start, but will be shut down by a fault condition.)
The kick start and bias circuits provide power for the control circuitry
during power-up. The kick start circuitry is an RC oscillator which
emits a 200 ms pulse every 1.5 seconds. These pulses switch current
from the Input Rectifier through Q201 to charge C201. When the power
supply is up, a winding on T103 provides power to the control circuitry.
This voltage is high enough to keep Q201 turned off.
1. Monitor the waveforms at TP206 and TP208 simultaneously on an
oscilloscope.
2. If the signal at TP208 goes high before the signal at TP206 goes low,
an overcurrent condition has been detected. Suspect a short in the
secondary (output rectifier, voltage regulators, or another assembly).

Low Voltage Supplies

1. Connect the negative lead of a DVM to A6TP301.
2. Check A6TP302 for +15 Vdc.
3. Check A6TP303 for −15 Vdc.
4. Check A6TP304 for +28 Vdc.
5. Check A6TP305 for −12.6 Vdc.
6. Check A6TP308 for +5 Vdc.
7. If the voltages measured above are correct but the power supply
LEDs on the A2 controller assembly are not lit, check W1.
8. If the voltages are low, disconnect W1 from A6J1 and measure the
test point voltages again. Unless a dummy load is connected to the
A6 power supply, the voltages should return to their nominal
voltages but be unregulated.
9. If the voltages do not return to near their nominal range, the A6
power supply is probably at fault.
10.If the +5 V supply is low, suspect the +5 V regulator or the feedback
circuit. To check the feedback circuit, measure the voltage of the
+5 V reference (U305 pin 6) and the ±5 V references to the voltage
regulators (U306B pin 7 and U306D pin 14).
11.Check output of U306A pin 1. If the feedback circuit is working
properly, the output of U306A should be near +13 Vdc.
Chapter 13
Display/Power Supply Section
A6 Power Supply Assembly
661