Profesora

Index & Warnings
Technical Specifications, Test Procedures & Adjustments
Wiring Connections
Inputs & Protections, Power Supply and Display Boards
Power Amplifier Board
Part List, Layout

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GENERALMUSIC S.p.A. Sales Division: 47842 S.Giovanni in Marignano (RN) ITALY - Via delle Rose, 12 - tel. 0541/959511 - tlx 550555 GMUSIC I - fax 0541/957404

SERVICE MANUAL

Notice
Service must becarried out by qualified personnel only. Any tampering carried out by unqualified personnel during the guarantee
period will forfeit the right to guarantee.
For a correct operation of the instrument, after having switched off, be careful to wait at least 3 seconds before switching on again.
To improve the device's specifications, the schematic diagrams may be subject to change without prior notice.Schematic Diagrams

Schematic Notes
All components marked by this symbol have special safety characteristics, when replacing any of these components use only
manufacturer's specified parts.
The (µ) micro symbol of capacitance value is substituted by U. The (Ω) omega symbol of resistance value is substituted by E.
The electrolytic capacitors are 25Vdc rated voltage unless otherwise specified. Allresistors are 1/4W unless otherwise specified.
Soldering point.

CODE : 277318

Supply voltage.

Male connector.

Logic supply ground.

Female connector.

Analog supply ground.

M/F faston connector.

Signal ground.

Test point.

Chassis ground.

ATTENTION
Observe precautions when handling
electrostatic sensitive devices

Flag joined with one or more flags with the same signal name inscribed.

1t483x44x310mm (1U)

µ Before proceed to supply the amplifier check visually the internal assembly, if appears an evident damage find the most possible reasons that
cause it.

Weight:

8Kg

µ Check the wiring cables for possible interruptions or shorts.

Power Requirements: (230Vac±10% 50Hz)

300VA

µ If the damage has burnt a printed circuit board don’t try to repair it,
replace with a new one.TECHNICAL SPECIFICATIONS
Dimensions:

Output Power:

(WxHxD)

(8Ω stereo/parallel)

2x 150Watts
98Vpp

Input Sensitivity:

(constant sensitivity)

0.775Vrms (0dB)

Test Instruments

(constant gain)

1.75Vrms (+7dB)

µ Audio Generator

(balanced)

30KΩ

µ Dual Trace Oscilloscope

(unbalanced)

15KΩ

µ Digital Multimeter

(constant sensitivity)

33±0.5dB

µ 4Ω 500W, 8Ω 300W, 100Ω 10W resistors(constant gain)

26±0.5dB

µ Variac (0÷250Vac)

Voltage Gain:

25V/µS

Slew Rate:
Damping Factor:

(8Ω stereo/parallel)

>400

Frequency Response

(-0.2dB)

20Hz÷20KHz

at Full Power:

(-3dB)

10Hz÷60KHz

IMD:

(SMPTE 60Hz/7KHz 4:1)

<0.1%

THD:

(THD+N)

<0.1%

S/N Ratio:

(unweighted)

>95dB

Crosstalk:

(1KHz)

>70dB

TEST PROCEDURES & ADJUSTMENTS
Precaution
µ To prevent short circuit during anytest, the oscilloscope must be
insulated,
EARTH insulated this occurs because some test require to connect its
probe to the amplifier output, non-compliance may cause damages to
oscilloscope inputs circuitry.
µ Before removing or installing any modules and connectors, disconnect
the amplifier from AC MAINS and measure the DC supply voltages
across each of the power suppliy capacitors. If yourmeasurement on any
of the caps is greater than 10Vdc, connect a 100 Ω 10W resistor across
the applicable caps to discharge them for your safety. Remember to
remove the discharge resistor immediately after discharging caps. Do not
connected.
power up the amplifier with the discharge resistor connected
µ Read these notes entirely before proceeding to any operation. These
notes are not comprehensive of alldamages that possibly occur, but
includes some specifically advices, checks and adjustments relative to
this amplifier.

Remarks
µ The power supply utilizes a dual bipolar DC rail configuration with low and
high voltages; one positive and one negative low rail (+/-Vcc1) and one
positive and one negative high rail (+/-Vcc2).

Visual Check
µ Use compressed air to clear dust in the amplifier...