Power Supply Assembly - HP 9020 Service Manual

4-54
Assembly Access
Power Supply Assembly
WARNING
ENSURE THAT POWER SWITCH IS OFF AND THAT COMPUTER
POWER CORD IS UNPLUGGED FROM AC OUTLET BEFORE RE-
MOVING POWER SUPPLY.
1. UNPLUG COMPUTER POWER CORD FROM AC OUTLET.
2. Remove front and rear covers from computer as previously described.
WARNING
WHEN POWER SUPPLY IS REMOVED FROM COMPUTER YOU
ARE EXPOSED TO LETHAL VOLTAGE FROM POWER SUPPLY
CAPACITORS. DISCHARGE POWER SUPPLY CAPACITORS
ACCORDING TO THE FOLLOWING STEPS. FAILURE TO FOL-
LOW THESE PROCEDURES COULD RESULT IN INJURY OR
DEATH.
3. Familiarize yourself with the power supply discharge tooL
HP
PN 09855-67004, if you have
not previously used it. The discharge tool consists of a meter and a switch-operated dischar-
ger. The meter indicates the approximate voltage across the energy storage capacitors in the
power supply.
WARNING
WHEN PERFORMING THE NEXT STEP. ENSURE THAT NO MET-
AL OBJECTS ARE IN YOUR HAND OR ON THE POWER SUPPLY.
THE DISCHARGE TOOL PINS WILL HAVE HIGH VOLTAGE
ACROSS THEM.
4. Carefully insert discharge tool pins directly into SAFETY DISCHARGE holes on top of
power supply until tool rests on power supply lid (Figure 4-57). Little force is required
if
tool
is straight when inserted. The meter gives an approximate indication of voltage across
capacitors.
WARNING
ALTHOUGH THE DISCHARGE TOOL SWITCH CAN BE MOVED
IN EITHER DIRECTION, THE TOOL DISCHARGES THE SUPPLY
ONLY WHEN THE SWITCH IS PUSHED DOWN.