Main Module Removal; Static Checks; Checkout/Adjustment Procedures - Crown CE-1000A Service Manual

Rev. D
Step 1: Acquire all information possible from the person(s)
having the problem to determine the nature of the com-
plaint. Ask questions like "Why was the amplifier brought in
for repair?" "Does it do this at turn on, does it take a while,
or does it only happen sometimes?" If you observe nothing
wrong, inquire tactfully how the unit was being used when
the malfunction occurred. This will help determine if the unit
may have been misused, if the user misunderstood what
happened, or if another system component may be at fault.
Remember, this is one of the first amplifier series to have
only Neutrik Speakon ® connectors for the outputs. There is
room for error in assembling the connectors. Be sure to ask
if the person may have had problems with the Speakons.
Step 2: Always do a complete visual inspection. A problem
may be obvious just by looking at the unit. Things to look
for include burned components, wires not connected, fan
obstructions, loose hardware or connections, and solder-
ing. Plugged heatsinks can greatly reduce amplifier effi-
ciency. The fan blades should spin freely. Burns and other
physical damage should be repaired and components in
the affected circuit areas should be checked carefully be-
fore continuing.
Whether a problem is identified by visual inspection or not,
several checks should be performed prior to turning the
amplifier on. These should be performed if any of the follow-
ing problems have been reported: catastrophic failure, no
signal output with constantly blinking Fault LED, or the con-
dition of the amplifier is otherwise unknown but failure is
suspected.
The third step on the "to do" list involves a number of elec-
trical checks. Due to the protection features of the CE-Series
amplifiers, it should be safe to turn-on under all circum-
stances, but these preliminary checks may allow a partial (if
not complete) repair before power is ever applied. These
checks are designed to find problems in the output stages.
The ultimate guide should always be common sense.

2.3.2 Main Module Removal

1. Remove the top cover by removing the four side screws,
lift up slightly on the rear of the cover, and then pull it toward
the back of the amplifier. Many of the parts are located on
the bottom side of the circuit board. In most situations, the
circuit board won't need to be removed from the chassis. In
the event that it does, go to step 2.
2. Remove the red and blue wires from the rectifier block
that is screwed to the bottom of the chassis near the power
supply capacitors and short the wires together through a
resistor such as a 300-ohm 10 W.
3. Disconnect the in-line FASTON that connects the circuit
board to the transformer.
CE Series Service Manual
4. Disconnect the 4-wire connector from the circuit board
that comes from the transformer.
5. Disconnect the small white wire that connects the circuit
board to the rectifier block.
6. Remove the four screws that hold the input assembly to
the chassis. Unplug the input assembly from the ribbon
cable.
7. Remove the four screws that hold the output jacks to the
back panel.
8. Unplug the fan from the circuit board.
9. Remove the eight screws (five in the rear, three in the
front) that hold the circuit board down to the chassis.
10. Remove the knobs from the gain pots by pulling the
knobs out the front. The circuit board will now lift out of the
chassis; but be careful, it is a tight fit.

2.3.3 Static Checks

1. Locate the flyback diodes D114, D115, D214, and D215
on the main modules and check for indications of a short. If
a short is indicated, this means that an output device or
driver transistor in parallel with that diode is shorted, usually
not the diode itself. If an output device is found to be defec-
tive, emitter resistors should also be checked. If no output
device is found defective, perform a quick check of driver,
pre-driver, and bias transistors. Then, if no problem is found,
move to the power-on checks in Section 2.3
2. Check driver and pre-driver transistors for shorts or opens.
If a fault is found, do an in-circuit static check of all semicon-
ductors on the output modules. If no output device and
nothing upstream is found defective, move to power-on
checks. Otherwise continue.
3. If a failure has occurred anywhere in the output stages,
check the bias servo transistor. Any failure associated with
bias transistors may result in repeat failure of the affected
channel even if all other defective components have been
found and replaced.
4. If a failure is found in any LVAs, checks should continue
up to the voltage translator stage.
5. Failure within the power supply itself is very rare; how-
ever, a cursory check of major items is always prudent.

2.4 Checkout/Adjustment Procedures

The following instructions outline an orderly checkout and
troubleshooting procedure. The purpose and arrangement
of this procedure is to ensure proper operation after a repair
has been completed. Before beginning these power-on tests,
review all cautions and warnings in Section 2.1, and perform
the checks listed in Section 2.2. These checks will minimize
the possibility of receiving a nasty surprise when turning on
the CE-Series amplifier.
WARNING! Most adjustments are made with the cover removed.
Maintenance 2-2