A6 Power Supply Assembly

The HP 8560A uses a switching power supply operating at 40 kHz to supply the low voltages for most of the analyzer hardware and a 30 kHz switching supply (CRT Supply) to provide the high voltages for the CRT display. The CRT Supply will be treated as a separate supply since the remainder of A6 must be operating for the CRT Supply to operate.

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

1.5seconds. 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.

Warning The A6 Power Supply and A6Al High Voltage Assemblies contain lethal voltages with lethal currents in all areas. Use extreme care when servicing these assemblies. Always disconnect the power cord from the instrument before servicing these assemblies. Failure to follow this precaution can present a shock hazard which may result in personal injury.

Warning The voltage potential at A6AlW3 is +9 kV. Disconnect at the CRT with caution! Failure to properly discharge A6AlW3 may result in severe electrical shock to personnel and damage to the instrument. See Chapter 3, Procedure 2.

Warning Always use an isolation transformer when troubleshooting either the A6 Power Supply or the A6Al HV Module. When using an isolation transformer, connect a jumper between AGTPlOl and A6TP301. This connects the circuit common to earth ground. Remove this jumper when the isolation transformer is not used.

Dead Power Supply

1.Connect the negative lead of a DVM to A6TP301.

2.Check TP308 for j-5 V.

3.Check TP302 for +15 V.

4.Check TP303 for -15 V.

5.Check TP304 for f28 V.

6.Check TP305 for -12.6 V.

7.Measure the voltage at TP108 to verify the output of the Input Rectifier. The voltage should be between +215 Vdc and +350 Vdc.

8.If it is not within this range, check the Input Rectifier, Input Filter, and the rear-panel line voltage selector switch.

9.Measure the voltage at TP206 to verify the output of the Kick- Start/Bias-Circuitry. The voltage should be approximately +14 Vdc.

10.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.

Display/Power Supply Section 12-11