A2 High Voltage Power Supply Circuit Theory; High Voltage Power Supply Troubleshooting - HP 5501B Operating And Service Manual

s. +15V SUPPLY UNBALANCE LED should turn on at a maximum of +16.6 Volts.
t. Adjust +15 Volt supply to +13 Volts.
u. -15V SUPPLY UNBALANCE should turn on at a maximum of +13.4 Volts.
v. Readjust ±15 Volt supplies to 15V ± 0.3 Volts.

8-87. A2 HIGH VOLTAGE POWER SUPPLY CIRCUIT THEORY

8-88. The High Voltage Power Supply (Figure 8-18) receives -15V from the system power supplies
through A1F2 and A1Q3. A1R11 and A1R12 set the high voltage output current limit. 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). The High Voltage Power Supply switch also
requires the +5 Volt supply (see Figure 8-18).
NEVER REMOVE A1J4 WITH THE HIGH VOLTAGE SUPPLY ON.
DANGEROUS HIGH VOLTAGE EXISTS.

8-89. HIGH VOLTAGE POWER SUPPLY TROUBLESHOOTING

LASER RADIATION IS ACCESSIBLE WHEN THE HP5501B COVERS
ARE REMOVED AND THE TEST-NORM SWITCH A1S2 IN THE TEST
POSITION.
FROM 1.2 KILOVOLTS TO 12 KILOVOLTS DC IS PRESENT ON THE
ANODE OF THE LASER TUBE IN THE HP5501B. 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.
8-90. Various conditions result from a faulty HV power supply.
a. No laser light is emitted.
1. Check that A1S2 is set to NORM when HP5501B covers are on or TEST when the
covers are off.
2. Check high voltage connectors (A1J3 and A1J4).
3. Check voltage at transistor A1Q3's emitter. With High Voltage Power Supply on, this
voltage should approach zero.
4. Check that A1F1 and A1F2 are OK and that the 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.
HP5501B
Service
8-29