6-9 REMOVING AND
REPLACING THE A18 OR
A19 PCB
This paragraph provides instructions for removing and replacing the
A18 Power Supply PCB or the A19 AC Line Conditioner PCB, both of
which are located in the power supply housing assembly (see Figure
6-3).
Preliminary Disconnect the power cord from the unit and remove
the top cover as described in paragraph 6-2.
WARNING
When power is removed from the instrument, always allow
five minutes for the capacitors on the A21 Line Filter/Recti-
fier PCB to discharge before removing either the A18 or A19
PCB.
Procedure Remove and replace the A18 or A19 PCB as follows:
Step 1 Remove the power supply cover and set it
aside.
Step 2 If the A19 PCB is being removed, (1) dis-
connect the cable assembly from the A21
Line Filter/Rectifier PCB at A19P2 and
(2) remove the Nylatch fastener used to
secure the PCB to the housing assembly.
Step 3 Lift up the edge tabs on the PCB and lift
it out of the power supply housing.
Step 4 Toreplace the PCB, reverse the removal
process.

6-12 682XXB/683XXB MM

REMOVAL AND A18 OR

REPLACEMENT PROCEDURES A19 PCB