Bose FreeSpace IZA 2120-HZ Service Manual page 121

ZA 2120-HZ Amplifier Tests
Required Equipment:
• Audio Precision ATS-1 or equivalent
• Audio Precision AUX-0025 digital filter or equivalent
®
• Bose Volume Control User Interface (PC 041966)
• 2 - 42 ohm (for 70V units) or 83 ohm (for 100V units), 250 Watt load resistors
Test Setup
• Output gain trim set to max.
•
Output mode set to "DUAL", unless otherwise specified.
•
Load 42 ohms/ch for 70V and 83 ohms/ch for 100V output.
•
Auto standby switch set to "OFF"
• All measure including power amp needs add an AUX-0025 Filter.
70V Output Mode Tests
•
Set the 70V / 100V output switch to 70V output.
• Connect the amplifier outputs to 42 ohm, 250W loads.
1. Output Gain Test
1.1 Place the Input Mode switch to the Dual position.
1.2 Apply a 1kHz, -2.5dBV sine wave to the RCA input jacks.
1.3 Measure the output level. Verify that it is +37.0dBV +/- 0.5 dBV.
1.4 Measure the THD+N level. Verify that it is < 0.3%.
2. Frequency Response Test
2.1 Apply a -23dBV, 1kHz sine wave to the RCA input jacks. Adjust the signal input level to
provide a 1W output across the 42 ohm loads. Reference a dB meter to this output level.
2.2 Change the input frequency to 55Hz. Measure the output level. Verify that it is -3dBr
+/- 1dBr.
2.3 Change the input frequency to 18kHz. Measure the output level. Verify that it is -1.5dBr
+/- 1dBr.
3. Signal to Noise Test
3.1 Apply a -2.5dbV, 1kHz sine wave to the input RCA jacks. Verify that you have a 120W output
from both channels.
3.2 Measure the signal-to-noise level, using a 20kHz filter and A-weighting. Verify that it is
> 88dBV.
TEST PROCEDURES
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