Free Audio Service Manuals - Free download harman kardon ca 240 service manual

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CA240

SPECIFICATIONS

Power Output, RMS 1 40 watts per channel into
4 Ohms, 20 ~ 20,000Hz
: 50 watts per channel into
2 Ohms, 20 ~ 20,000Hz
: 100 watts bridged mono into
4 Ohms, 20 ~ 20,000HZ
HCC (High Instantaneous: i25A
Current Capability)
THD (4 Ohms/2 Ohms) : No more than 0.1%/0.2%
Negative Feedback : 25dB
Power Bandwidth 2 10Hz to 100,000Hz
Frequency Response : 10Hz to 100,000Hz +0, --3dB
Signal-to-Noise Ratio : 80dB
Input Sensitivity : 0.25 ~ 3V Adjustable
Active Crossover Characteristics
High Pass : 200Hz, 12dB/Octave
Low Pass : 200H2, 12dB/Octave

Power Supply : DC +13.8V (11 ~ 16V usable),
negative ground
Typical Input Current Requirements
At Idle : 1.9A
Full Power Music Signal: 4A (4 Ohms/ch.)
: 6A (2 Ohms/ch.)
: 12A (4 Ohms/ch.)
: 18A (2 Ohms/ch.)
Dimensions (W x H x D) I 12-1/4"x2-11/16"x8"
(310 x 68 x 203 mm)
: 5 lbs. 12 oz. (2.6 kg)

Full Power Sine Wave

Weight

Speciﬁcations and components subject to change without notice.
Overall performance will be maintained or improved.

DISASSEMBLY PROCEDURES (REFER TO PAGES 4 AND 8)

m CABINET BOTTOM (143) REMOVAL
Remove 6 screws 0 and remove the Cabinet Bottom
(143).

L2 MAIN (PCB-1) AND FILTER (PCB-2) P.C. BOARDS
REMOVAL
1. Remove the Cabinet Bottom (143). (Refer to step

m.)

2. Remove the Insulator (159).

3. Remove 11 screws i3 and remove the Frame (141)
with Bracket (162).

4. Remove 10 screws 0 and remove the Main P.C.
Board (PCB»1) with Filter P.C. Board (PCB»2). If
necessary, unsolder the lead wires.

ALIGNMENT PROCEDURES (REFER TO PAGES 7 AND 8)

Conditions:
0 Connect a 13.8V power supply to the 12V BATTERY
POWER IN terminal.

IDLING CURRENT ADJUSTMENT

0 After the power on, wait for 5 minutes before
measuring to be sure of the most stable operation.

Step Connection Equipments Adjustment For
1 Connect the DC voltmeter to TPI (+) and TP2 (-). VR401 33mV
2 Connect the DC voltmeter to TPS (+) and TP4 (-). VR402 33mV

After the adjustment is complete, let the unit settle down for 10 minutes, than double-check that the idling current is set

properly.

CIRCUIT DESCRIPTION

General Description of the CA240 Power Supply

The power supply voltages for the Power Amplifier are
generated by means of a switching power supply. The
switching power supply consists of transformer L2,
transistors 05 through 09, transformer T1 and bridge
rectifiers D12 through 016. This switching power supply
is connected to associated circuits which control the
initial turn on delay, thermal protection and load
protection.

Circuit Description of Switching Power Supply

Under normal operating conditions the collector of 02 is
+8.1 volts and O3 and 04 are turned off.

Assume switching transistors 05 and 06 are initially
turned on by a base current which is supplied through
R13, D7 and the L2 secondary winding. The collector
currents of 05 and 06 will flow through one of the L2

primary windings and one-half of the T1 primary
winding thereby generating a voltage in the T1 feedback
winding.

This voltage causes a current to flow through the L2
secondary winding via R17 and the center tap of L2.
This current also flows through the base emittor junc-
tions of 05 and 06, DB, D9 and 09. This current keeps
05 and 06 on.

The purpose of DB, D9 and 09 is to develop a negative
bias voltage which speeds up the switching time of 05
through 08. The voltage across the L2 secondary
winding continues to rise until core L2 saturates. At the
moment L2 saturates the voltage generated by the L2
secondary winding reverses, 05 and 06 are turned off
and Q7 and 08 are turned on. This causes a current to
flow in the opposite half of the T1 primary winding. The

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