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Technical Specifications; Bias Adjustement; Adjustment Procedure; Block Diagram - LEM K3 Active Service Manual

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TECHNICAL SPECIFICATIONS

POWER (EIA RS-426A)
Watts EIA
HANDLING
Watts IHF
DISTORTION
(THD+N)
INPUT
kohms
IMPEDANCE
kohms
INPUT SENSITIVITY
dB
POWER SUPPLY
SENSITIVITY (SPL 1W/1m)
dB
MAX SPL continous
dB
MAX SPL peak
dB
FREQUENCY RESPONSE
Hz (-10dB)
DISPERSION ANGLE (OxV)
°
CROSSOVER FREQUENCY
Hz
HIGH
COMPONENTS
LOW
CONSTRUCTION
CONTROLS
CONNECTIONS
DIMENSION
mm (WxHxD)
WEIGHT
kg

BIAS ADJUSTEMENT

Instruments, materials and tools:
Instruments, materials and tools:
Instruments, materials and tools:
Instruments, materials and tools:
Instruments, materials and tools:
- Audio Generator
- Dual Trace Oscilloscope with 10x prober.
- Digital Voltmeter (or Multimeter)
- 8Ω 1000W Resistor
- Temperature Meter
Setup:
Setup:
Setup:
Setup:
Setup:
- Connect the Audio Generator to the input and set it to output 1KHz sinusoidal signal.
- Connect the Dual Trace Oscilloscope to the input (set CH1trace at 0.5V/div. 200usec./div) and to the output (set CH2 trace at 20V/div.
200usec/div) of the amplifier.
WARNING: The oscilloscope must be earth insulated.
WARNING: The oscilloscope must be earth insulated.
WARNING: The oscilloscope must be earth insulated.
WARNING: The oscilloscope must be earth insulated.
WARNING: The oscilloscope must be earth insulated.
- Insert the temperature sensor through the interstize between the heatsink and R15 (PTC).
- Unconnect amplifier's output from the cross-over and connect the 8Ω 1000W resistor instead of it.
- Insert the voltmeter terminals across R22.

ADJUSTMENT PROCEDURE

ADJUSTMENT PROCEDURE
ADJUSTMENT PROCEDURE
ADJUSTMENT PROCEDURE
ADJUSTMENT PROCEDURE
1) Turn on the amplifier.
2) Set the input signal to obtain approximatelly 120Vpp on the output.
3) When the temperature has reaches about 50°C (122°F) set the input level to minimum
4) Adjust the trimmer VR1 to read a voltage of 3±0.05mV on the multimeter.
5) Check that the voltage across the R74 resistor has the same value.
6) At the same temperature condition, adjust the VR2 trimmer to read 4±0.05mV across R26 resistor.
7) Check that the voltage on the R78 resistor has the same value.
Verifing:
Verifing:
Verifing:
Verifing:
Verifing:
1) Increase the input level to obtain an output voltage about of 0.5Vpp.
2) Check with the oscilloscope that the output signal is without a cross-talk distortion and eventually slightly adjust the VR1 position until
distortion disappears.
(Note: the voltage value across the R22 and across R74 resistor must not exceed 5mV)
3) Re-connect the cooling fan and the crossover instead of the 8Ω 1000W resistor.
❏ ❏ ❏ ❏ ❏ 2 2 2 2 2
K 3 Active
K 6 Active
300
550
350
600
<0,02%
<0,02%
30 balanced
31 balanced
15 unbalanced
15 unbalanced
0 (0,775 V)
0 (0,775 V)
230Vac +/-15% 50-60Hz
230Vac +/-15% 50-60Hz
115Vac +/-15% 50-60Hz
115Vac +/-15% 50-60Hz
100
100
121
124
124
127
60-20000
50-20000
60x60
60x60
1,8kHz at 12-18dB/oct.
1,4kHz at 12-18dB/oct.
1" driver coaxial
1.5" driver coaxial
12" woofer
15" woofer
Cabinet: birch polywood.
Finish: Black scratch-resistant paint
Metal Grille
Polyurethane front panel
Volume Control.
SHIELD
Limiter ON/OFF.
Combo - 1 XLR-M
POWERCON power connector
542x496x537
542x656x537
36
47

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This manual is also suitable for:

K6 active