Crown Macro-Tech MA-5002VZ Service Manual page 40

MA-5002VZ Service Manual
Type of Test
or Adjustment
24. Intermodulation
Distortion (I.M.D.)
CH 1 VZ MODE SWITCH
VZ-ODEP
*On Original Control Module
LOCK LOW
Q42930-0 this was the
VZ (AUTO)
LOCK HIGH position.
VZ (AUTO)*
Figure 5.4 VZ Mode Switch Locations
5-12 Maintenance
Input Signal and
Load Parameters
I.M. Signal Source
8-ohm Load
CH 2 VZ MODE SWITCH
LEVEL
15
12 18
l 0
9 21
6 24
3 27
CH2 0 30 ENABLE
VZ (AUTO)*
VZ (AUTO)
LOCK LOW
VZ-ODEP
Comments
Next configure the amp for parallel mono operation.
With the input signal now present on channel one only,
load channel one output with 8 ohms and channel
two with 2 ohms. Observe that channel two ODEP
protection circuit is limiting both channel one and
channel two outputs. Next load channel one with 2
ohms and channel two with 8 ohms. Observe that
channel one ODEP protection circuit is limiting both
channel one and channel two outputs.
Return the cooling fan blade to normal operation af-
ter these tests have been completed, and allow a few
minutes for the amplifier to cool with no signal input.
Return all controls to initial conditions per Section
5.4.1.
Correct operation of the ODEP circuit is dependent
upon correct ODEP null settings (Step 6).
Place the sensitivity switches in the 26 dB position.
Use a 60-Hz/7-kHz (standard SMPTE IM signal) input
signal summed in a 4:1 ratio. Set the 60-Hz portion
for 73.8 Vrms at the output of the channel under test.
This is your 0 dB reference. Measure the I.M. distor-
tion. Check in –5 dB (power) steps until –35 dB is
reached (range is 1,065 W down to 0.34 W). Read-
ings should be less than .05% at each level.
Figure 5.5 ODEP Protection
130446-1 Rev. A
©2000 Crown International, Inc.