QSC K.2 Series Service Manual page 34

Part 1: General checks (power up, mute delay, and turn-on sequence)
The purpose of these steps is to remove any previous settings saved in the amplifier so we can test without any modifi-
cations done to the EQ. We will also verify the proper power up sequence. If the amplifier module's power LEDs or LCD
screen continually blink during power up, there may be an issue with the power supply or amplifier section.
1. Using a variac, slowly increase the AC voltage going into the amplifier while monitoring the AC current. Maximum cur-
rent should be no greater than 0.5▲A at 120▲V or 0.3▲A at 230▲V.
Note: The amplifier module should come out of protect above 85Vac in 6 seconds or less. The dead voltage range is
135V - 165V. Abort the test if the amplifier draws excessive AC current.
2. Verify the blue power indicator is lit and home screen is displayed on the LCD screen.
3. Reset the K.2 module to factory default: HOME Menu -> SETTINGS -> FACTORY RESET -> YES
4. Turn the unit off and observe that all of the LEDs go off.
5. Turn the unit on and observe the turn-on sequence:
• Verify the Blue LED and LCD screen turn on within 3 seconds or less.
• In the next second, verify the LCD is displaying information on screen.
• In the next 2 seconds, listen for a relay click (120▲V only).
• Finally, verify the fan does not spin (if temperature is less than 50C).
6. Verify the amplifier is running with default settings.
Part 2: Verifying Ch.1 (LF): 2 OHM POWER vs. DISTORTION at 400Hz.
1. Set the output of function generator: 0.55▲Vrms, 400▲Hz, sine wave.
2. Turn the gain control of inputs Ch.A, B, and C to the minimum (counter-clockwise).
3. Feed the function generator's output to input Ch.A.
4. Apply a 2▲Ω load to Ch.1 (LF)
5. Slowly turn the gain control A to maximum while checking the power measurement; it should be approximately 250
watts, +/-50 watts with less than or equal to 0.1% THD.
6. Turn the gain control A to minimum and repeat steps 3 through 5 with input Ch.B.
Part 3: Ch.1 short circuit and 2 ohm load recovery (150 WATTS, 1% THD, 2.8A@120V).
1. Set the output of function generator: 0.45▲Vrms, 1▲kHz, sine wave.
2. Turn the gain control of inputs Ch.A, B, and C to minimum (counter-clockwise).
3. Apply a 2▲Ω load to Ch.1 (LF).
4. Feed the generator's output to input Ch.A and turn the gain control A to maximum (clockwise).
5. Verify output power; it should be approximately 150 watts, +/-50 watts.
6. Apply a short to Ch.1 (LF) output and verify short limit protection.
Note: The PSU may shut down intermittently before it can run steadily and safely in output short condition.
7. Verify the AC line current draw; it should drop below 1.0A.
8. Remove the short and verify the amplifier module recovers into 2▲Ω.
9. Turn the gain control A to minimum and continue next test.
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