Odep Limiting; Lf Protection; Signal To Noise Ratio; Turn On Transients - Crown Macro-Tech MA-3600VZ Service Manual

MA-3600VZ Service Manual
Procedure Torture: Load each channel with the
primary (red and black leads) of a PSU transformer
(D 7040-5). Inject a 35 Hz sine wave for an output
level of 89.5 Vrms, for 10 seconds.
Procedure Short: Inject a 60 Hz sine wave with 30.0
VAC at the amplilfi er output. After establishing signal,
short the output for 10 seconds.
4.3.15 Test 14: ODEP Limiting
Spec: ODEP Limiting occurs per the procedure.
Either channel controls limiting in Parallel Mono
Mode.
Initial Conditions: Controls per standard; rag or
other obstruction blocking fan so that it does not
turn.
Procedure: Load the amplifi er to 2 ohms on each
channel. Inject a 60 Hz sine wave and adjust for
30 Vrms at the output. After a few minutes observe
a wave form similar to Figure 4.4. Both positive
and negative alternations must show the distinctive
waveform. There is no requirement of symmetry
between positive and negative alternations. There is
no requirement of uniformity from channel to channel.
Remove the input signal from both channels and
allow the amplifi er to cool for a few minutes. Switch
the amplifi er to Parallel Mono and remove the load
from Channel 1. Inject the signal into Channel 1 and
observe that ODEP limiting occurs at the output of
both channels. Remove the load from Channel 2, and
install the load on Channel 1. Again, observe that both
channels limit. Return all amplifi er controls to standard
initial conditions. Remove the fan obstruction.
4.3.16 Test 15: LF Protection
Spec: Amplifi er mutes for low frequency.
Initial Conditions: Controls per standard.
Procedure: No load. Inject a 0.5 Hz, 10 volt peak-to-
peak, square wave, or a 1Hz, 17 volt peak-to-peak,
sine wave into each channel and verify that each
channel cycles into mute.
4.3.17 Test 16: Signal to Noise Ratio
Spec: 100 dB below rated 8 ohm power 20 Hz to 20
kHz. 105 dB A-Weighted.
Initial Conditions: 26dB Sensitivity. Short inputs.
Procedure: Load each channel to 8 ohms. Measure
less than 950 µV at the output of each channel (20
Hz-20 kHz bandpass fi lter).
Mantenance 4-4
4.3.18 Test 17: Turn On Transients
Spec: No dangerous transients.
Initial Conditions: Controls per standard.
Procedure: From an off condition, turn on the amplifi er
and monitor the output noise at the time of turn on.
Note: Turn on noise may increase signifi cantly if the
amplifi er is cycled off and on.
4.3.19 Test 18: Turn Off Transients
Spec: No dangerous transients.
Initial Conditions: Controls per standard.
Procedure: From an on condition, turn off the amplifi er
and monitor the output noise at the time of turn off.
Note: Turn off noise may increase signifi cantly if the
amplifi er is cycled off and on.
4.3.20 Test 19: Intermodulation Distortion
Spec at 0 dB Output: 0.02%.
Spec at –35 dB Output: 0.05%.
Initial Conditions: Controls per standard.
Procedure: Load each channel to 8 ohms. Inject a
SMPTE standard IM signal (60 Hz and 7 kHz sine
wave mixed at 4:1 ratio). Set the 60 Hz portion of the
sine wave to 72 Volt RMS. Set the 7 kHz portion to
25%. With an IM analyzer measure less than 0.02%
IMD. Repeat test at –35 dB (reference 72 Volt RMS, 60
Hz portion) and measure less than 0.05% IMD.
4.3.21 Test 20: High Line Cutout
Spec: 10% - 12% above nominal.
Initial Conditions: Controls per standard.
Procedure: Using an AC line variac, increase the
line voltage until the unit goes into standby. The
unit should fo into standby at 10% - 12% above the
nominal (120V U.S. units).
4.3.22 Post Testing
After completion of testing, if all tests are satisfactory,
the amplifier controls should be returned to the
positions required by customer. If conditions are
unknown or unspecified, factory settings are as
follows:
Level Controls: 9 to 11 O'Clock.
Sensitivity Switch: 0.775V U.S., 1.4V International.
Stereo/Mono Switch: Stereo.
Ground Lift: Lift.
Power: Off.
130366-1 Rev. A
©2000 Crown International, Inc.