Crown ce 4000, Руководство по обслуживанию

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Maintenance 4-7
130485-1 Rev. B
CE 4000 Service Manual
©2002 Crown Audio, Inc.
If you don’t observe anything wrong with the amplifi er,
tactfully inquire how the owner used it and try to
determine if it was misused or some other component
in their system could have been at fault. Remember
that the protection circuits in this amplifi er will protect
loudspeakers from problems caused upstream from
the amplifi er (DC protect).
If you lack suffi cient information about the problem,
and there aren’t any obvious problems with the
amplifi er, skip to Section 4.6, the Electrical Checkout
Procedures.
4.4.5 Identifying and Repairing the Cause
The fi rst step in identifying the cause of the problem
is always a visual inspection. Once the top cover
is removed, and the supplies are discharged, look
for loose connectors, broken wires, loose hardware,
burnt components, or bad solder joints on the PC
boards. Check both sides of the board.
Once the visual inspection is complete you may
power up the unit. The best way to positively locate
which PWA is at fault is to have a working PWA of each
type on hand and plug them into the amplifi er one at
a time to see when the problem goes away.
The following Symptoms and Causes may help you
determine which corrective action to take. We realize
that this list is limited. Please read through the Theory
chapter in this manual to better understand the
function of each PWA. This will help you come to your
own conclusion as to the location of the problem.
Amp does not appear to power up. No Enable
LED.
First, check the power supply fuse (located on the
Line Filter PWA). Check for faulty switch or faulty
inductor connection in the EMI and Filter module.
Also, make sure the AC line voltage is correct for the
amplifi er you are working on. Severely low AC line
voltage could cause the amp to not power up. If
both check out, then the amplifi er is in a fault mode.
Viper could be dead. The most likely trouble area
is the Flyback PWA.
The Fault LEDs on one or both channels are
fl ashing.
1. The Fault LEDs normally flash during turn-on
delay. Wait for six seconds to see if the LED stops
fl ashing.
2. One or more of the power supplies are out of
tolerance or missing. Replace or troubleshoot the
Flyback PWA. If this does not correct the problem,
check for the 400 V Vboost by measuring from TP251
to TP50. If it is low, then troubleshoot the PFC boost
stage. If 400 V is o.k., check the ±Vccs at L6 and
L9. They should measure approximately 105 VDC to
ground. If Vcc is low or missing, troubleshoot the Full
Bridge DC to DC converter stage.
3. ±15 V supply is too low. Check the Flyback PWA.
4. DC is present on the Channel 1 or Channel 2
output terminals, usually caused by a bad MOSFET
or diode in the amplifi er’s output stage.
5. The channel one heatsink is too hot. Verify the
heatsink temperature is less than 80°C. The output
heatsinks should be at earth ground. The SMPS
reference heatsink is above ground, so
do not touch
amplifi er ground and the SMPS reference heatsink
at the same time.
6. The overvoltage sensor has been tripped. Measure
the ±Vccs at L6 and L9. They should read less than
120 VDC referenced to ground.
7. Transformer T1 has exceeded its thermal limit.
Replace T1. Replace R713.
Signal LED is off and the Clip LED is on for either
channel.
1. Troubleshoot the appropriate channel. A Clip LED
on generally means an output stage failure.
Signal LED is on and the Clip LED is on for either
channel.
1. The amplifier channel is clipping. Reduce the
input signal level
2. A short is present at the output. Check the output
wiring.
Output sounds distorted. Clip LED is off.
1. The input stage is being overdriven. Reduce the
input signal level.
2. There is a problem in the Input PWA. Replace or
troubleshoot the Input PWA.
Amplifi er does not meet Output Power specifi ca-
tion.
1. The amplifi er has reached thermal limits. Check
for proper fan operation.
2. PFC boost stage is not functioning properly.
Check for 400 VDC at TP-251 with respect to TP-50.
Troubleshoot PFC boost stage if measurement is
nonconforming.
Amplifier does not meet Frequency Response
specifi cation.
1. Make sure the output voltage does not exceed
45Vrms.
2. Check back panel fi lter switch positions.
3. Check BFG PWA highpass and lowpass circuitry.
4. Possible problem in the 32-kHz 7th-order Gaussian
fi lter. Readjust R178 and R278 for channel 1 and 2