HP 8562E, Service Manual

Page: 463 / 482

1. Measure the voltage at TP108 to verify the output of the input rectifier. The voltage
should be between Vdc and Vdc.
2. If it is not within this range, check the rear panel fuse, input rectifier, input filter, and the
rear-panel line voltage selector switch.
3. Measure the voltage at TP206 to verify the output of the kick-start circuitry. The voltage
should be approximately Vdc.
4. 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), is probably shorted.
5. If there are pulses at TP206, or there are pulses at TP210, but not at TP206, the buck
regulator control circuitry is probably faulty.
1. Disconnect the power cord from the spectrum analyzer.
2. Connect the positive output of a current-limited dc power supply to the cathode of
(J7 pin 2) and the ground to J7 pin 1.
3. Set the current limit of the power supply to about 500 and the voltage to 12 Vdc.
4. Make sure a jumper is connected from to This independently powers
the buck regulator control circuitry.
5. Connect a jumper from the dc power supply Vdc output to the positive end of
nearest
6. Connect a jumper from Vdc output to the end of physically nearest
7. If the current draw exceeds approximately 50 suspect a short in the buck regulator
control circuitry, or a shorted CR201, or a shorted (Shorted components may be
hot
8. Check TP204 for an 80 sawtooth (4 Vp-p). Suspect if it is not present.
9. Check TP203 and TP207 for 40 square (12 Vp-p). The waveform edges should be
sharp. Compare the waveform to the inputs of pins 6 and 7. If the waveforms at
either TP203 or TP207 are bad, one of the in the DC-DC converter is probably
defective.
10. Check TP105 and TP106 for a 12 Vp-p sawtooth waveform that is flattened at the
bottom. If the waveform is a squarewave, the FET to which the test point is connected
has failed or shorted.
11. Check TP202 for 80 pulses (12 Vp-p).
12. Short the leads of CR108. Check TP103 for 80 pulses of about 11 V peak-to-peak.
13.
Remove the short from CR108. The voltage of the lower side of the pulses should float up
to about 4.5 V. If not, suspect that CR108 is shorted.
14. If the waveform at TP202 is correct but the waveform at TP103 is bad, suspect either
Q102 or U132. (The waveform should have sharp edges.)
Display/Power Supply Section 13-13