HP 6268B Operating And Service Manual

Table 5-8. Checks and Adjustments Required After Semiconductor Replacement (Continued)
REFERENCE
FUNCTION OR CIRCUIT
CHECK
ADJUST
A4CR105
and
A4CR106
Reverse voltage protection.
Output voltage.
—
VR1
Voltage clamp circuit.
CC load regulation.
—
VR40
Mixer amplifier stabilization
diode.
CV transient response.
R47 (See para. 5-98).
VR60, VR61
Reference regulator.
+6.2V and -6.2V reference voltages.
—
VR90
Crowbar.
Trip voltage.
R95, A5R125 (See
para. 5-104 and 5-106).
5-60 Disassembly Procedures
5-61 The following seven paragraphs describe the
procedures for removing and disassembling the five sub-
assemblies in this supply. These procedures are referred to
throughout the manual where necessary.
5-62 A1 Main Circuit Board Removal. To remove the
main printed circuit board, proceed as follows:
a. Disconnect input power and remove top cover from
supply.
b. Remove six hold-down screws visible on component
side of main circuit board.
c. Unplug board from receptacle mounted on inter¬
connection circuit board by gently pulling on finger hole
in opposite end of circuit board. Only finger hole should
be used to remove board; do not pull on board-mounted
components to aid removal. Take care that rear barrier
strip clears opening in rear panel.
5-63 A5 Front Panel Removal. To remove the front
panel, proceed as follows:
a. Disconnect input power, turn supply upside down,
and remove four screws holding handles to front panel.
b. The front panel may now be swung outward, hinging
on wires to circuit breaker. Access is provided to all panel-
mounted components.
5-64 Main Filter Capacitor Bank Removal. To remove
the main filter capacitors (Cl 01 through Cl 03, C104, or
C105 depending on the power supply model), proceed as
follows:
a. Disconnect input power and remove top and bottom
covers from the supply.
b. Remove the long flat-head screws and V-shaped
clamps that hold the main filter capacitors in place.
Sufficient lead length is provided to allow capacitors to be
lifted partially out of instrument.
5-65 A2 RFI Filter Assembly Removal. To remove the
RFI assembly, proceed as follows:
a. Disconnect input power, turn supply upside down,
and remove bottom cover.
b. Remove four screws holding RFI heat sink to mount¬
ing brackets.
c. Lift out RFI assembly and turn over.
d. Remove four screws holding cover to heat sink.
This allows access to the internal components and 11 5V/
230V jumpers.
5-66 A4 Heat Sink Removal. In order to gain access
to the following components, it is necessary to remove
the heat sink assembly: Transistors A4Q101 through
A4Q110; diodes A4CR101 through A4CR108, and
A4CR110; resistors A4R106, A4R123, and A4R150
through A4R165; capacitors A4C1 through A4C5; cooling
fan A4B1; and thermal switch A4TS101. For the location
of these components, see Figures 7-5 and 7-6. To remove
the heat sink assembly, proceed as follows:
a. Disconnect input power from the supply, stand it on
its left side, and remove top and bottom cover.
b. Remove main printed circuit board as described
in paragraph 5-62.
c. Remove two screws holding upper edge of heat
sink to upper chassis flange (marked "A" in Figure 7-4 ).
d. Disengage two pins holding lower section of heat
sink assembly to main circuit board support tray by
sliding heat sink down about 1 /2 inch and slightly away
from chassis. Before fully removing heat sink assembly,
observe lead dress so assembly may be returned easily to
correct position.
e. Maneuver heat sink assembly downwards and away
5-15

HP 6268B Specifications

General

Brand	HP
Model	6268B
Category	Power Supply
Language	English