8-87. The High Voltage Power Supply
(Figure 8-17)
receives +15V from the system power supplies through
A1F1. The laser discharge current passes through the high-voltage connector and ballast resistor to the laser
anode and from the laser cathode to A1J4 (Pin 1).
WARNING
NEVER REMOVE A1J4 WITH THE HIGH VOLTAGE SUPPLY ON.
DANGEROUS HIGH VOLTAGE EXISTS.
8-88. HIGH VOLTAGE POWER SUPPLY TROUBLESHOOTING
WARNING
FROM 1.2 KILOVOLTS TO 12 KILOVOLTS DC IS PRESENT ON THE
ANODE OF THE LASER TUBE IN THE HP 5517B. EXERCISE EXTREME
CAUTION WHEN WORKING INSIDE THE INSTRUMENT. THE HIGH
VOLTAGE COULD CAUSE SERIOUS PERSONAL INJURY IF
CONTACTED. ANY MAINTENANCE SHOULD BE PERFORMED BY
SERVICE TRAINED PERSONNEL ONLY.
8-89. Various conditions result from a faulty HV power supply.
a. No laser light is emitted.
1. Check high voltage connectors (A1J3 and A1J4).
2. Check that A1F1 and A1F2 are OK and that the measured voltages are +15V and -15V respectively.
If rear panel LASER ON LED is on but the laser beam remains off, there is a high probability that the HVPS is
defective.
3. Turn the power off and disconnect the high voltage connector. Carefully connect a high voltage
probe. (You will need to make a jumper to extend the probe into the high voltage connector.)
4. Turn power back on and perform an open circuit voltage test. The voltage should be between 10 kV
and 12 kV. If not, replace the high voltage power supply, if the laser still doesn't work then replace
the laser tube assembly.
WARNING
AFTER TESTING, THE POWER SUPPLY MAY TAKE UP TO 3 MINUTES
FOR THE OPEN-CIRCUIT VOLTAGE TO DECAY. THEREFORE, SHORT
ANODE TO GROUND IMMEDIATELY.
b. Laser light is emitted but flashes or causes a REF Error.
1. Turn power off and disconnect A1J4. Insert a 1 K, 1%, 0.5 Watt resistor (Rt) between the J4 (Pin 1)
connector. [Leave J4 (Pin 2) disconnected].
2. Connect an oscilloscope across Rt-
3. Turn on power and allow the laser head to warm up.
4. Observe DC test voltage. It should be between 3 and 4 Volts, if not, perform the current adjustment
procedure in paragraph 5-18 of this manual.
5. Set the oscilloscope to view the AC component and calculate the percent ripple. There should be less
than 3% ripple in the test voltage. If not, replace the HV power supply. If the ballast resistor is bad,
the test voltage might be an aperiodic intermittent voltage. If this is the case, replace laser tube
assembly.
6. Disconnect external ±15 Volt power supplies from laser head.
7. Remove resistor Rt and replace connector to A1J4.
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