Removal And Replacement; Top Cover Removal; Gaining Access To Assemblies In The Supply; Gpib Board Removal - Agilent Technologies 6622A Service Manual

j. Use a mildly activated rosin core solder (such as Alpha
Metal Reliacor No. 1, Agilent Part No. 8090-0098) for
repair. The flux residue of this type of solder can be left
on the printed-circuit board. Generally, it is safer not to
clean the printed-circuit board after repair. Do not use
Freon or other types of spray cleaners. If necessary, the
printed-circuit board can be brushed using a natural-
bristle brush only. Do not use nylon-bristle or other
synthetic-bristle brushes. Do not use high-velocity air
blowers (unless ionized).
k. Keep the work area free of non-conductive objects such
as Styrofoam-type
ethylene bags, and plastic wrappers. Non-conductive
devices that are necessary in the area can be kept from
building up a static charge by spraying them with an
anti-static chemical (Agilent Part No. 8500-3397).
i. Do not allow long hair to come in contact with static-
sensitive assemblies.
4-3

REMOVAL AND REPLACEMENT

The major assemblies within the power supply are
illustrated in Figure 4-1. The major differences between the
models are the quantity and type of output boards they
contain. the 80 Watt Output boards are about twice the size
of the 40 Watt Output boards. Figure 4-1 shows the board
configuration for each model. Component location diagrams
and functional schematics for the individual assemblies are
given in Section VI. Replaceable electrical and mechanical
parts for all models are listed in Section V. The following
paragraphs provide instructions for removing certain
assemblies and components for which the procedure may
not be obvious upon inspection. Replacement procedures
are essentially the same as the corresponding removal
procedure except that they are performed in the reverse
order.
To avoid the possibility of personal injury, remove the
power supply from operation before removing the covers.
Turn off ac power and disconnect the line cord, G PIB
cable, loads, and remote sense leads before attempting
any repair or replacement.
Most of the attaching hardware is metric. Use of other
types of fasteners will damage threaded inserts. When
removing or installing screws, use a No. 1 or a No. 2
Pozidriv screwdriver.
4-4

Top Cover Removal

The top cover must be removed to gain access to the
assemblies inside the supply. To remove the cover, proceed
as follows:
a. Remove the four screws which hold the carrying straps.
cups, polystyrenefoam,
b. Spread the bottom rear of the cover slightly and pull
back to disengage it from the front panel.
c. Remove the top cover. Note that you can use the top
cover assembly as a support when you open the top
chassis in the next procedure.
4-5 Gaining Access to Assemblies in the
Supply
As shown in Figure 4-1, each power supply model contains
an GPIB board and at least two output boards. The output
poly-
boards are mounted on an upper chassis assembly and in
the lower section of the main chassis. The upper chassis
assembly is hinged and its output boards are mounted with
the components facing down. The output board(s) in the
main chassis are mounted with the components facing up.
To gain access to the output boards, the GPIB board, power
transformer, and other components inside the supply,
proceed as follows:
a. Remove four screws located on top of the chassis near
the front.
b. Remove three screws from top left side and two screws
from rear which hold the upper chassis to the main
chassis.
c. Open the hinged upper chassis by lifting it from the left
side. This will give you access to the components on the
output board(s) mounted in the hinged upper chassis as
well as those mounted in the lower main chassis. Be
sure to avoid any cable snag when opening the hinged
chassis.
d. Place the removed top cover assembly under the
opened upper chassis for support.
4-6

GPIB Board Removal

Looking at the unit from the front, the GPIB board is
located on the right side with its components facing to the
left. Most of the components are accessible for test purposes
without removing the board from the unit. However, for
easy access it is best to remove the board from the unit. To
remove the GPIB board, proceed as follows:
a. Disconnect all cables. Note the routing of cables if they
have to be removed since their position may affect the
supply's ripple performance.
b. Remove two hex standoffs from rear which secure the
GPIB connector to the chassis. Retain the lock or flat
washers for reassembly.
c. Remove one ground screw from the top front of the
GPIB board. Retain lock or flat washers for reassembly.
d. Slide board forward approximately 1/4 inch to
disengage the keyed standoffs.
e. Lift board out of chassis.
4-7 40 Watt output hoard Removal
Model 6623A has two 40 Watt Output boards located in the
main chassis and Models 6624A and 6627A have four 40
Watt Output boards; two boards are mounted in the upper
chassis assembly and two are mounted in the main chassis.
To remove a 40 Watt Output boards, proceed as follows:
4-2