MA-5002VZ Service Manual
5-6 Maintenance
130446-1 Rev. A
©2000 Crown International, Inc.
Bias voltage is set while the amplifier is at room tem-
perature. If the amplifier is hot from prior testing for
repair or other purposes, it should be set aside until it
has cooled before continuing with this check. Bias,
once factory set, normally will not require adjustment.
For channel 1: Measure the voltage at TP1 pin 15 with
respect to pin 13 (DO NOT measure from ground ref-
erence). The bias voltage should equal .330VDC ±
10 millivolts. If the bias voltage needs to be adjusted,
adjust R556 on the channel 1 output assembly for the
correct bias voltage. For channel 2: Measure the volt-
age at TP2 pin 15 with respect to pin 13 (DO NOT
measure from ground reference). The bias voltage
should equal .330VDC ± 10 millivolts. If the bias volt-
age needs to be adjusted, adjust R556 on the chan-
nel 2 output assembly for the correct bias voltage.
ODEP Nulls are based on heatsink temperatures. A
reference voltage is supplied at TP1/TP2 which is pro-
portional to the heatsink temperature. For positive
ODEP: Measure TP1/TP2 pin 18 with respect to
ground. Refer to the chart (Figure 5.1) below. If mea-
sured voltage falls outside the listed range, the am-
plifier is too hot or too cold. Now measure TP1/TP2
pin 11 and adjust, if necessary, R182/R282 for the set
voltage on the chart, ±0.1 V. For negative ODEP: Mea-
sure TP1/TP2 pin 17 with respect to ground. Refer to
the chart (Figure 5.1) below. If measured voltage falls
outside the listed range, the amplifier is too hot or too
cold. Now measure TP1/TP2 pin 9 and adjust, if nec-
essary, R191/R291 for the set voltage on the chart,
±0.1 V. Note that the negative ODEP set voltage is a
negative voltage with respect to ground.
5. Low Side Bias No Signal
No Load
6. O.D.E.P Null No Signal
No Load
Figure 5.1 ODEP Set Voltage Chart
Type of Test Input Signal and Comments
or Adjustment Load Parameters
Voltage
Measured
ODEP Set
Voltage
2.90 V
2.91 V
2.92 V
2.93 V
2.94 V
2.95 V
2.96 V
2.97 V
2.98 V
2.99 V
12.96 V
12.64 V
12.72 V
12.60 V
12.48 V
12.36 V
12.24 V
12.12 V
12.00 V
11.88 V
Voltage
Measured
ODEP Set
Voltage
3.00 V
3.01 V
3.02 V
3.03 V
3.04 V
3.05 V
3.06 V
3.07 V
3.08 V
3.09 V
11.76 V
11.64 V
11.52 V
11.40 V
11.28 V
11.16 V
11.04 V
10.92 V
10.80 V
10.68 V
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