HP 8568B manual High-Voltage Adjustment SN 3001A and Below, Description

2.High-Voltage Adjustment (SN 3001A and Below)

Note

2. High-Voltage Adjustment (SN 3001A and Below)

This procedure is for IF-Display Sections with serial number prefixes 3001A and below. The procedure for serial prefixes 3004A and above is located immediately after this procedure.

Note This procedure should be performed whenever the AlAll High Voltage Multiplier, AlVl CRT, or AlA High Voltage Regulator Assembly is repaired or replaced.

Reference IF-Display Section:

AlA Z-Axis Amplifier

AlA High-Voltage Regulator

AlA f15 V Regulator

AlA + 100 V, +5.2 V Regulator

Description

Warning This procedure is intended for adjustment purposes only. Voltages are present which, if contacted, could cause serious personal injury. Approximately -4000 V dc can be present on the AlA High Voltage assembly even when the ac line cord is disconnected. Do not attempt to remove the AlA High-Voltage Assembly from the instrument. Do not disconnect the CRT’s post-accelerator cable; the CRT can hold a + 18 kV dc charge for several days.

If for any reason the AlA High Voltage Assembly or the post accelerator cable must be removed, refer to “Discharge Procedure for High Voltage and CRT” at the end of this adjustment procedure.

A 1OOO:l divider probe is used to measure the CRT cathode voltage. First, the high-voltage probe is calibrated by comparing measurements of the + 100 V dc supply voltage with and without the probe. Any measurement error due to the use of the high-voltage probe is calculated into the adjustment specification of the CRT cathode voltage, which is adjusted with the AlA HV ADJUST control. When the CRT cathode voltage is properly adjusted, the CRT filament voltage will be +4.45 f0.04 V rms measured with CRT beam at cut-off, which is required for maximum CRT life. The filament voltage is referenced to the high-voltage cathode and can only be measured directly with special equipment.

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