HP 6269B Operator’s, Organizational, Direct Support And General Support Maintenance Manua L page 47

TM 11-6625-2958-14&P
are arrowed "E" and "F" in Figure 7-1.) Lifting
brackets away from heat sink allows access to
triac A2CR1. A magnetized screwdriver is useful
in performing this step.
5-68 Heat Sink (A 4) Removal. In order to gain ac-
cess to the following components, it is necessary
to remove the heat sink assembly. Transistors
A4Q101 through A4Q108; diodes A4CR1OI through
A4CR106, A4CR108, and A4CR110; resistors
A4R106, A4R123, and A4R150 through A4R155; ca-
pacitors A4C1 through A4C5; cooling fan A4B1; and
thermal switch A4TS101.
components, see Figures 7-5, 7-6, 7-7, and 7-8.
To remove the heat sink assembly, proceed as fol-
lows:
a.
Unplug unit, stand it on left side, and
remove top and bottom covers.
b. Remove main printed circuit board as
described in Paragraph 5-64.
Remove two screws holding upper edge
c.
of heat sink to upper chassis flange (arrowed "E"
and "F" in Figure 7-D).
d. Disengage two pins holding lower sec-
tion of heat sink assembly to main circuit board
support tray by sliding heat sink down about ½
inch and slightly away from chassis. Before fully
removing heat sink assembly, observe lead dress
so assembly may be returned easily to correct po-
s it ion.
e. Maneuver heat sink assembly down-
wards and away from chassis until it is resting on
table (sufficient lead length is provided). Gentle
leverage with a thin screwdriver may be necessary
to allow heat sink assembly to clear upper chassis
Access is now provided to all components
flange.
mounted on heat sink except resistors A4R150
through A4R155, and A4R123,
5-69 Heat Sink (4) Disassembly. To gain access
to resistors A4R123 and A4R150 through A4R155
(shown in Figures 7-6 and 7-8) it is necessary to
disassemble the heat sink assembly by utilizing
the following procedure:
a. Remove heat sink assembly as described
in Paragraph 5-68 above.
b. Turn supply upside down and place heat
sink assembly partially into chassis so fan (A4B1)
is protruding above chassis.
Remove four screws and four shoulder
c.
washers attaching fan mounting plate to heat sink.
Do not remove fan from mounting plate. When re-
assembling heat sink, do not overtighten these
screws. Too much tension will damage the insu-
lating rods.
d. Remove two screws holding current sam-
pling resister A4R123 to topmost two portions of
heat sink.
If necessary, the resistor may be
For the location of these
unsoldered at this point.
e. Remove mounting nuts from A4CR106 on
left side of heat sink, and from A4CR108 on right
side of heat sink.
and shoulder washers on transistor A4Q102 on right
side of heat sink (see Figure 7-5).
f. Slide top section of heat sink forward and
off insulating rods.
Remove four screws holding emitter re-
9.
sistor circuit board to bottom half of heat sink. A
magnetized screwdriver is useful here. Access is
now provided to series regulator emitter resistors
A4R150 through A4R155 (see Figure 7- 6).
h. If necessary to completely remove emit-
ter resistor circuit board, unsolder connections to
board, marking wires to enable correct replacement,
and remove board.
5-70 Interconnection Circuit Board (A3) Removal.
To replace capacitor A3C3 or transformer A3T2,
(shown in Figure 7- 2), it is necessary to remove
the interconnection circuit board by utilizing the
following procedure:
a. Remove main circuit board, RFI assembly,
and heat sink assembly as described in Paragraphs
5-64, 5-67, and 5-68 respectively.
b. Remove six screws holding back panel to
chassis frame.
c. Stand supply on left side, and remove
two screws holding main circuit board support tray
to back panel. Move panel away from frame.
d. Remove two screws holding main circuit
board support tray to internal chassis divider.
Working from top rear of supply, inter-
e,
connection circuit board (still attached to main
circuit board support tray) can be angled up enough
to allow access.
f. If necessary to completely remove inter-
connection circuit board, remove two screws hold-
ing board to support tray, one screw holding ca-
pacitor clamp (A3C3) to support tray, and two
screws holding bias transformer (A3T2) to support
tray. Unsolder connections to board, marking
wires to enable correct replacement, and remove
board.
5-71 REPAIR AND REPLACEMENT
5-72 Section VI of this manual contains a list of
replaceable parts.
not have a standard manufacturers' part number, it
is a "special" part and must be obtained directly
from Hewlett-Packard. After replacing a semicon-
ductor device, refer to Table 5-8 for checks and
adjustments that may be necessary. All compo-
nents listed in Table 5-8 without A-designators are
on the main printed circuit board (Al).
5-16
Remove mounting nuts, bolts
If the part to be replaced does