Discharging Instructions; Back Panel - Crown PSA-2 Service Manual

following procedure is omitted. The visual inspection can
be performed in 10 to 15 minutes. It is recommended both
as a preventive maintenance procedure and also for its
value in determining cause of malfunction.
1) Check that all external screws are tight and that
none are missing.
2) Check all fuses/circuit breakers.
3) Check for smooth and proper operation of
switches, etc.
4) Inspect line cord for possible damage to cap, jacket
and conductors.
5) Remove protective covers as outlined in
disassembly instruction (Section 7.6).
6) Check that all attaching parts for internal circuits
are tight and that none are missing.
7) Inspect all wiring for charred insulation, or
discoloration as evidence of previous overheating.
8) Check that all electrical connections are secure.
This includes wire terminals, screw and stud type
terminals, and all soldered connections.
9) Check for obvious destruction of internal structural
parts, Distortion in any of these parts could mean that
the unit has been dropped or subjected to severe shock.
Fig. 7.17 Discharge Points
7-8
7.5 Discharging Instructions
Both the PSA-2 and SA2 amplifiers incorporate very
large-storage capacitors in the power supply (C101,
C201, C102, C202). For this reason, at any time the
covers are removed it is necessary to discharge the power
supply capacitors in order to avoid possible damage to
the unit and also to prevent shock hazard. This is best
performed by placing a 50 ohm/ 10 watt resistor across
the main trace that surrounds the Crown logo (See Fig.
7.17) of the NPN and PNP output modules (do this on
each channel). Another method is to place this same
value resistor across the terminals of each of the four
power capacitors. No matter which method is used, use
extreme caution when handling the discharge device.
7.6 Disassembly for Inspection,
Service, Testing, Adjustment and Repair
for the PSA-2/8A2
The extent of disassembly required will depend upon the
extent of inspection, service, testing, adjustment and
repair to be performed. Illustrations referred to in
parenthesis (index numbers) are located in the parts list
(Section 6) of this manual
A. Cover Removal
A fairly complete visual inspection can be performed by
removing the top (102) and bottom (101) covers. To
remove these parts, proceed as follows:
1. Remove the three top cover phillips head screws
(107), located nearest to the front panel
2, Next, remove the three back panel phillips head
screws and respective star washers (106) located
nearest the top of the unit.
3. Remove the two (one each side) phillips head
screws and respective star washers (106,109) centrally
located between the side panel air vents.
sently lift the rear of the top cover (102) with
fingers placed on each side, through the air vent holes.
5. After complete removal of the top cover, the four
output module boards, the main module circuit board
and the power supply logic module board should be
exposed
To remove the bottom cover:
1. Place the unit bottom side up.
2. Remove the nine phillips head mounting screws
and respective lockwashers (106,109) from the
bottom cover.
3. Remove the four (two on each side) phillips head
mounting screws and respective star washers (106)
located nearest to the unit, gently lift and remove the
cover. When the bottom cover is completely removed,
the following components are exposed: the power
transformer, power capacitors, output terminal
module, relay module, fan package, mother board,
input connector module, anti-pop module (on earlier
units) and on the PSA-2, the balanced input module.
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