Idling Current Adjustment - Electro-Voice P 1201 Service Manual

1. Operating Voltage:
2. Operating Voltage Deviation Range: -30% .... +10%
3. Power Consumption
- Driven with sine signal f = 1kHz
Idling Power Consumption
Maximum Power Consumption (RL=4Ω)
Nominal Power Consumption (RL=4Ω)
Standard Power Consumption (RL=4Ω)
Power Consumption at 1/8 of the Max. Output Power
Power Consumption at 1/8 of the Max. Output Power
at 10 % Mains Overvoltage
4. Settings/Adjustments

4.1. IDLING CURRENT ADJUSTMENT

Connect a DC-voltmeter to the BIAS measuring points (on the printed board assembly 84194/2 / 84199/2, see
service connectors) and adjust the idling current via the trimmers VR101 / VR301 (on the printed board assembly
84194/1 /84199/1). Adjustment has to be performed for HOT / COLD U(DC) = 7.5mV and at normal room
temperature. If the power amplifier has previously been operated, it has to be given several hours of time for
regaining normal temperature.
4.2. FLOATING - SYMMETRY
Checking and setting the floating voltage symmetry has to be performed immediately after adjusting the idling
current.
Operate the power amplifier in idling condition. Measuring between the measuring points CNS1X.1 / CNS2X.5
and CNS1X.5 / CNS2X.5 with a DC-voltmeter, set the floating voltage symmetrical to GROUND via VR1 on the
printed board assembly 84194/1 (84199/1).
The absolute voltage value is not critical but the symmetry of the ± floating voltage over GROUND.
Checking the set floating voltage is possibly by use of a DC-voltmeter and measuring between on the service
connector between CNS2X.3 and CNS2X.5 on the printed board assembly 84194/2 (84199/2) as well as on the pin
terminal between CN10.1 and CN10.2/3 on the printed board assembly 84194/1 (84199/1).
The measured DC voltage value should be 0 volts.
4.3. VCA - OFFSET
Rhythmically open and short-circuit the pin contacts CNS2X.1 and CNS2X.2 on the printed board assembly
84194/2 (84199/2). Use VR100 to adjust the power amplifier output to their minimum offset value (with
oscilloscope to minimal peak value or to the audible minimum volume of the interfering pulse).
5. Function Test
5.1. OUTPUT – Offset Voltage
DC-measurement at the loudspeaker outputs with U(DC) ≤ ±10mV.
5.2. LIMITER
5.2.1. Attenuation Test
Power amplifier driven with a 1 kHz signal up to U(A) = 69 V (without load). Increase the input voltage by
10dB. The LIMITER LED lights and the output voltage ascents by approximately 2dB to approximately 85 V
while slightly clipping. The distortion rate of the limited signal is at THD = 1.0 ... 1.5%. Further increasing the
input signal up to a value of +21dBu should not result in remarkably higher clipping.
5.2.2. Attack and Release Times
Test has to be performed without load resistors connected.
1.) Drive the power amplifier with a burst signal (f = 1kHz, 10 cycles, rate: ≈ 0.5 sec.) and U(E) = +16dBu at the
input.
U(B) = 230V 50Hz ... 60Hz / U(B) = 120V 50Hz ... 60Hz
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X1201 / P1201
50 - 70 W
1870 W
1730 W
590 W
720 W
870 W
Output Power
1200 W
1000 W
100 W
156 W
180 W