Crown PSA-2 - Page 76

crown
Warning
Immediately after removing the bottom cover as
previously described, discharge the four large capacitors
by connecting a 50 ohm resistor (not less than 10 watt
rating) across the terminals of each Output Assembly
trace (see Section 7.5). Failure to heed this warning could
result in serious shock or damage to circuit components
when handling modules.
Both the PSA-2 and SA2 have been specially designed for
ease of service. Most every component part is in fingers
reach for fast and effective replacement. This means it
should never be necessary to “replace” a board module
itself, unless for testing or if damage was done beyond
repair (severed, burnt, etc.). However in order to apply
standard repair procedures, it may be necessary to
temporarily remove a board module. If so, observe the
following procedures.
B. Main Board Module Removal
1, Remove the top cover (102) as described in
Section A. Locate main module (See Fig. 7.18).
2. Disconnect the four pin input cable by
simply applying upward pressure on the plug casing.
For future reconnection, note the location of pin No.1.
3. Release the main support of the board by pushing
the four retaining clips outward, while simultaneously
lifting the board beyond the clips retention points.
4. At this point, apply equal upward pressure along
the edge of the board which has inter-connect pins
labeled 6 through A. The board will come free as soon
as each of these pins are released.
MAIN MODULE
LOW VOLTAGE POWER SUPPLY MODULE
CH.1 NPN OUTPUT MODULE
CH.1 PNP OUTPUT MODULE
gO DP
—. CH.2 PNP OUTPUT MODULE
F. CH.2 NPN OUTPUT MODULE
G. DISPLAY MODULE
D.
Power Supply/ Logic Module Removal
1. Remove the top cover (102) as described in
Section A. Locate the power supply module (See
Fig.7.18).
2. Release the main support of the board by pushing
the two retaining clips outward, while simultaneously
lifting the board beyond the clips retention points.
3. Apply equal upward pressure along the edge of
the board which has interconnect pins labled A
through W. The board will come free as soon as each
of these pins are released.
PNP/NPN Output Module Assembly Removal
(Including output transistor replacement)
pozEsr
1. Remove the top cover (102) as described in
Section A. Locate the output assembly(s) which must
be removed (See Fig. 7.18).
2. Remove the four phillips head mounting screws
(69) being careful not to damage the delicate heat
sink (68) fins.
3. Apply equal upward pressure on each short end
of the assembly until it is released.
4. If it is necessary to replace an output device,
desoldering of the transistor leads as well as screw-
nut-washer removal must be performed.
5. To replace U300 (LM334H Thermal Sense IC),
remove all four output and driver transistors from
the assembly. At that point, the board can be removed
from the heat sink fins exposing U300.
RELAY MODULE
MOTHER BOARD MODULE
OUTPUT TERMINAL MODULE
ANTI-POP MODULE (EARLIER UNITS ONLY)
INPUT CONNECTOR MODULE
CH. 2 POWER TRANSFORMER
PSA-2 BALANCED INPUT MODULE
POWER SUPPLY CAPACITOR ASSEMBLY
FAN ASSEMBLY 7-9
Fig. 7.18 Component Location Diagram