Agilent Technologies 8564EC, Service Manual

Page: 499 / 512

658 Chapter 13
Display/Power Supply Section
A6 Power Supply Assembly
A6 Power Supply Assembly
8564EC , and 8565EC spectrum analyzers use a
switching power supply operating at 40 kHz to supply the low voltages
for most of the analyzer hardware.
Kick starting occurs when there is a fault either on the power supply or
on one of the other assemblies. The power supply will try to start by
generating a 200 ms pulse ("kick") every 1.5 seconds. A kick-starting
power supply often appears to be dead, but the fan will make one or two
revolutions and stop every 1.5 seconds.
Dead Power Supply
1. Use an isolation transformer and connect a jumper between
A6TP101 and A6TP301.
2. Connect the negative lead of a DVM to A6TP301.
3. Check TP308 for +5 V.
4. Check TP302 for +15 V.
5. Check TP303 for
−
15 V.
6. Check TP304 for +28 V.
7. Check TP305 for
−
12.6 V.
8. Measure the voltage at TP108 to verify the output of the input
rectifier. The voltage should be b215 Vdc and +350 Vdc.
9. If it is not within this range, check the rear panel fuse, input
rectifier, input filter, and the rear panel line voltage selector switch.
10.Measure the voltage at TP206 to verify the output of the kick-
start/bias-circuitry. The voltage should be approxi14 Vdc.
Test point 206 is on pin 1 of U203.
11.If there is no voltage at TP206, check TP210 for pulses 200 ms wide
with an amplitude of 14.7 V. If there are no pulses present, the
kick-start circuitry is probably defective. If the pulses are low in
amplitude (about 1 V), Q201 is probably shorted.
12.If there are pulses at TP206, or there are pulses at TP210, but not at
TP206, the buck regulator control circuitry is probably faulty.