Leisure Craft P-500 Service manual
Index & Warnings
Technical Specifications, Test Procedures & Adjustments
Layout
Wiring Connections
Inputs Board, Supplies & Protections Board
Power Amplifier Board
Display Board & Part List
2
4
5
6
7
8
SERVICE MANUAL
Schematic Diagrams
CODE : 277319
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
Notice
Service must be carried out by qualified personnel only. Any tampering carried out by unqualified personnel during the 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.
period will forfeit the right to guarantee.
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. All resistors are 1/4W unless otherwise specified.
Soldering point.
Male connector.
Female connector.
M/F faston connector.
Test point.
Flag joined with one or more flags with the same signal name inscribed.
Supply voltage.
Logic supply ground.
Analog supply ground.
Signal ground.
Chassis ground.
Observe precautions when handling
ATTENTION
electrostatic sensitive devices
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TECHNICAL SPECIFICATIONSTECHNICAL SPECIFICATIONS
TECHNICAL SPECIFICATIONS
TECHNICAL SPECIFICATIONSTECHNICAL SPECIFICATIONS
Dimensions: (WxHxD) 483x88x325mm (2U)
Weight: 13Kg
Power Requirements: (230Vac±10% 50Hz) 500VA
Output Power: (4Ω stereo/parallel) 2x 300Watts
(8Ω stereo/parallel) 2x 200Watts
(8Ω bridge) 600Watts
(16Ω bridge) 400Watts
Max. Undistorted Out: (4Ω stereo/parallel) 98Vpp
(8Ω stereo/parallel) 113Vpp
RemarksRemarks
Remarks
RemarksRemarks
➭ 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 CheckVisual Check
Visual Check
Visual CheckVisual Check
➭ Use compressed air to clear dust in the amplifier chassis.
➭ Before proceed to supply the amplifier check visually the internal assem-
bly, if appears an evident damage find the most possible reasons that
cause it.
➭ Check the wiring cables for possible interruptions or shorts.
disconnect the supplies from the outputs modules (CN2, CN3 on POWER
AMPLIFIER boards), continue to check the supplies.
CAUTION: Before re-connecting the output modules to the supplies,CAUTION: Before re-connecting the output modules to the supplies,
➭
CAUTION: Before re-connecting the output modules to the supplies,
CAUTION: Before re-connecting the output modules to the supplies,CAUTION: Before re-connecting the output modules to the supplies,
you must have the capacitors discharged for your safety: connect ayou must have the capacitors discharged for your safety: connect a
you must have the capacitors discharged for your safety: connect a
you must have the capacitors discharged for your safety: connect ayou must have the capacitors discharged for your safety: connect a
100100
ΩΩ
20W resistor across the caps and remove the resistor just after 20W resistor across the caps and remove the resistor just after
100
Ω
20W resistor across the caps and remove the resistor just after
100100
ΩΩ
20W resistor across the caps and remove the resistor just after 20W resistor across the caps and remove the resistor just after
they are discharged.they are discharged.
they are discharged.
they are discharged.they are discharged.
➭ Finally verify the DC supplies on SUPPLIES & PROTECTIONS Board:
T8 (+Vcc2) =+61±2Vdc
T5 (+Vcc1) =+35±1.5Vdc
T6 (-Vcc1) =-35±1.5Vdc
T7 (-Vcc2) =-61±2Vdc
CN2 pin1 =+23±1Vdc
CN3 pin3-4-5 =+15±1Vdc
CN3 pin8-9-10 =-15±1Vdc
(8Ω bridge) 194Vpp
Input Sensitivity: (constant sensitivity) 0.775Vrms (0dB)
(constant gain) 1.75Vrms (+7dB)
Input Impedance: (balanced) 30KΩ
(unbalanced) 15KΩ
Voltage Gain: (constant sensitivity) 33±0.5dB
(constant gain) 26±0.5dB
Slew Rate: 25V/µS
Damping Factor: (4Ω stereo/parallel) >400
(8Ω stereo/parallel) >800
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) >60dB
TEST PROCEDURES & ADJUSTMENTSTEST PROCEDURES & ADJUSTMENTS
TEST PROCEDURES & ADJUSTMENTS
TEST PROCEDURES & ADJUSTMENTSTEST PROCEDURES & ADJUSTMENTS
PrecautionPrecaution
Precaution
PrecautionPrecaution
➭ To prevent short circuit during any test,
EARTH insulatedEARTH insulated
EARTH insulated, this occurs because some test require to connect its
EARTH insulatedEARTH insulated
probe to the amplifier output, non-compliance may cause damages to
oscilloscope inputs circuitry.
➭ Before removing or installing any modules and connectors,
the amplifier from AC MAINSthe amplifier from AC MAINS
the amplifier from AC MAINS and measure the DC supply voltages
the amplifier from AC MAINSthe amplifier from AC MAINS
across each of the power suppliy capacitors. If your measurement on any
of the caps is greater than 10Vdc, connect a 100Ω 20W resistor across
the applicable caps to discharge them for your safety. Remember to
remove the discharge resistor immediately after discharging caps.
power up the amplifier with the discharge resistor connectedpower up the amplifier with the discharge resistor connected
power up the amplifier with the discharge resistor connected.
power up the amplifier with the discharge resistor connectedpower up the amplifier with the discharge resistor connected
➭ Read these notes entirely before proceeding to any operation. These
notes are not comprehensive of all damages that possibly occur, but
includes some specifically advices, checks and adjustments relative to
this amplifier.
the oscilloscope must bethe oscilloscope must be
the oscilloscope must be
the oscilloscope must bethe oscilloscope must be
disconnectdisconnect
disconnect
disconnectdisconnect
Do notDo not
Do not
Do notDo not
➭ If the damage has burnt a printed circuit board don’t try to repair it, re-
place with a new one.
Test InstrumentsTest Instruments
Test Instruments
Test InstrumentsTest Instruments
➭ Audio Generator
➭ Dual Trace Oscilloscope
➭ Digital Multimeter
➭ 2Ω 1000W, 4Ω 500W, 100Ω 20W resistors
➭ Variac (0÷250Vac)
➭ Temperature Meter
SetupSetup
Setup
SetupSetup
➭ Connect the Variac between the mains and the amplifier and set it at zero
voltage.
➭ Set the amplifier in STEREO MODE and turn full clockwise the LEVEL
potentiometers.
➭ Connect the audio generator to the channel inputs and set it to 1KHz
775mV
➭ Insert the temperature meter through the IC3 interstice located at centre
of heatsink.
➭ The procedures that follow must be executed subsequently in the order
specified.
Supply CheckSupply Check
Supply Check
Supply CheckSupply Check
➭ Remove the transformer secondary fuses (located on SUPPLY & PRO-
TECTIONS board), set the Variac to the nominal mains voltage, check
with the Multimeter the AC supply voltages:
F1-F2=52±2Vac F3-F4=90±3Vac.
➭ Re-set the Variac at zero voltage, turn off the amplifier and put the fuses
back on its holders.
➭ Connect the oscilloscope probes CH1/2 to the channel outputs, before
RL1 and RL2, set both to 20V/div. 200µS/div.
➭ Set up the Variac slowly monitoring the Outputs with the oscilloscope
CH1/2 connected, it should display the sinusoidal input signal amplified
with no distortions, if a distortion occur check the POWER AMPLIFIER
boards as suggested in the ADVICES section.
➭ If the protection trips, turn off the amplifier, wait some minutes and
(0dB) sinusoidal signal.
RMS
➭ If one or more voltages don’t correspond, check the rectifiers, capacitors
and transformers disconnecting them from circuitry, refer to schematics.
Channels CheckChannels Check
Channels Check
Channels CheckChannels Check
➭ The channel A is facing the front and channel B the rear of the chassis.
➭ These procedures are intended for one channel at a time, repeat these
operation for the other channel.
➭ Verify, with the Multimeter, the insulation between the heatsink and the
transistors collectors.
SETUP:SETUP:
➭
SETUP:
SETUP:SETUP:
Connect the CH1 scope GND clip to CN3 pin 1 (GND terminal).
Connect the CH1 probe tip to CN3 pin 2 (AMP output).
Connect the CH2 probe tip to D20 cathode.
Set the LEVEL potentiometers full clockwise.
The load resistor is disconnected.
INITIAL TEST:INITIAL TEST:
➭
INITIAL TEST:
INITIAL TEST:INITIAL TEST:
Increase slowly the Variac. The channel output signals must be symmetrical respect the GND without visible distortion and oscillation as shown in
Fig.1 Trace A
proceed to check the other channel.
Verify that, when the heatsink temperature is less than 50°c, the cooling
fan voltage must be between 10 and 14Vdc.
HIGH RAIL CHECK:HIGH RAIL CHECK:
➭
HIGH RAIL CHECK:
HIGH RAIL CHECK:HIGH RAIL CHECK:
When the output signal (Positive half-wave) is less than 30Vp the voltage
on D20 cathode must remain constant at 36V, when the output signal
exceeds 30Vp the voltage must follow the output signal with 6V offset
(see
Fig.1 Trace B
D30 anode (see
Connect the 4Ω 500W load on the output and repeat the INITIAL and
HIGH RAIL checks.
Check the signal clipping, it must occur at 48±2Vpp (see
A,B,C
).
Fig. 1Fig. 1
Fig. 1
Fig. 1Fig. 1
. If there is a distortion read the section ADVICES and
), to check the negative high rail connect the probe to
Fig.1 Trace C
).
Fig.2 Trace
Trace B (20V/div.)
Trace A (20V/div.)
Trace C (20V/div.)
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22
2
22
Fig. 2Fig. 2
Fig. 2
Fig. 2Fig. 2
Trace B (20V/div.)
Trace A (20V/div.)
Trace C (20V/div.)
Verify the voltages across the diodes D19 and D26; they must be 14.8
±0.5Vdc.
SIGNAL/CLIP SENSOR CHECK:SIGNAL/CLIP SENSOR CHECK:
➭
SIGNAL/CLIP SENSOR CHECK:
SIGNAL/CLIP SENSOR CHECK:SIGNAL/CLIP SENSOR CHECK:
Set the LEVEL pot to minimum, set the scope timebase at 1V/div. 200µS/
div., then increase the level and check the SIGNAL/CLIP led activity: it
must turn on (green light) when the amplifier output is higher than 1Vp.
Set the scope at 20V/div. and increase the level, check the led: it must
change from green to red colour at the amplifier output signal clipping.
CURRENT AND SHORT CIRCUIT SENSOR CHECK:CURRENT AND SHORT CIRCUIT SENSOR CHECK:
➭
CURRENT AND SHORT CIRCUIT SENSOR CHECK:
CURRENT AND SHORT CIRCUIT SENSOR CHECK:CURRENT AND SHORT CIRCUIT SENSOR CHECK:
Set the CH2 sensitivity to 0.5V/div., connect the scope CH1, GND clip at
CN3 pin 2 (AMP output) and the probe tip at TR26 (PNP) emitter, connect the CH2 probe tip at TR17 (NPN) emitter.
Set the generator to have approx. 1Vp on the emitters: their difference
must be less than 0.2V on the peaks (see
Fig. 3Fig. 3
Fig. 3
Fig. 3Fig. 3
Fig.3 Trace A & B
Trace A (0.5V/div.)
Trace B (0.5V/div.)
).
Connect a 2Ω 1000W load. Increase the input signal, the output current
limiter must keep the emitter voltages (both half channel) at 1.25Vp
approx. (see
Fig.4 Trace A
).
Temporarily short the amplifier output: the current limiter must keep the
emitter voltages (both half channel) at 0.8±0.1Vp (see
Fig. 4Fig. 4
Fig. 4
Fig. 4Fig. 4
COOLING FAN & PROTECTION CHECK:COOLING FAN & PROTECTION CHECK:
➭
COOLING FAN & PROTECTION CHECK:
COOLING FAN & PROTECTION CHECK:COOLING FAN & PROTECTION CHECK:
Fig.4 Trace B
Trace A (0.5V/div.)
Trace B (0.5V/div.)
Short circuit pins 15 and 16 of OC1, the fan must run at max. speed
(20÷23Vdc on its tips).
Short circuit pins 13 and 14 of OC1, the PROTECT led must turn on
immediately, the fan must run at max. speed. The PROTECT led of the
other channel must also turn on after 2 Sec. and the relays must disconnect the output sockets.
Remove the short circuit, after 3 Sec. both PROTECT leds must turn off
and the relays must re-connect the output sockets.
Fig. 7Fig. 7
Fig. 7
Fig. 7Fig. 7
Temporarily short the emitter and the collector of TR1 the PROTECT led
must turn on and the relays must disconnect the output sockets.
Turn off the amplifier and wait a minute to let the supply caps discharge.
OFFSET SENSOR CHECK:OFFSET SENSOR CHECK:
➭
OFFSET SENSOR CHECK:
OFFSET SENSOR CHECK:OFFSET SENSOR CHECK:
Trace A (5V/div.)
Set the Variac to zero voltage output, disconnect the amplifier load and
the supply connection to the Power board (CN2,3,4), turn on the amplifier, connect temporarily (by means of a suitable conductor wire) CN3 pin
2 to +15Vdc (CN1 pin 5), the PROTECT led must turn on in 5 seconds
approx.; the fan must run at maximum speed).
Trace B (2V/div.)
Remove the connection, wait until the leds turn off and after some sec-
BIAS ADJUSTMENT:BIAS ADJUSTMENT:
➭
BIAS ADJUSTMENT:
onds repeat the check with -15Vdc (available on CN1 pin 4), the led
PROTECT must turn on again.
BIAS ADJUSTMENT:BIAS ADJUSTMENT:
Remove the CH2 probe, connect CH1 GND clip to CN3 pin 1 (GND
terminal) and its probe tip to CN3 pin 2 (AMP output) and set its sensitiv-
SOA ADJUSTMENT:SOA ADJUSTMENT:
➭
SOA ADJUSTMENT:
SOA ADJUSTMENT:SOA ADJUSTMENT:
Set the scope sensitivity at 5V/div. (both channels).
Disconnect the fan and cut the pins A-B of J16.
Connect the 4Ω 500W load and connect the CH2 probe tip at TR23
collector, check the waveform as shown in
Fig 5 Trace B, Trace A
CH1 that is also connected at TR26 (PNP) emitter.
Fig. 5Fig. 5
Fig. 5
Fig. 5Fig. 5
Trace A (5V/div.)
show
ity at 1V/div.
Set the generator level at zero, connect the Multimeter across
the emitters of TR17 and TR26, when the heatsink temperature reaches 55°C,
turn off the cooling fan and adjust R55 trimmer to read 6±0.5mV.
Adjust the generator level until the sinewave appears at full screen amplitude, No crossover distortion must be detectable: if necessary re-adjust
R55. Re-connect the fan.
BANDWIDTH CHECK:BANDWIDTH CHECK:
➭
BANDWIDTH CHECK:
BANDWIDTH CHECK:BANDWIDTH CHECK:
Sweep the generator frequency from 20Hz to 20KHz, the output level
must have not detectable level changes.
SLEW RATE CHECK:SLEW RATE CHECK:
➭
SLEW RATE CHECK:
SLEW RATE CHECK:SLEW RATE CHECK:
Set the scope sensitivity to 10V/div. 1µS/div. and set the generator to
1KHz square wave mode. Check the output square wave rising and falling
Trace B (5V/div.)
edge slopes: both must be 10V/µS or more as shown in
Fig. 8Fig. 8
Fig. 8
Fig. 8Fig. 8
Fig 8
.
Set the scope CH2 sensitivity at 2V/div. and connect the probe tip at the
testpoint TP3.
Set the load at 2Ω, wait until the temperature reaches 80°C; then change
Trace A (10V/div.)
the load back to 4Ω.
Adjust the generator level to have the CH1 waveshape as shown in
Trace A
.
Fig 6
Turn the R47 trimmer to level the peaks of the CH2 waveshape as shown
Fig 6 Trace b
Fig. 6Fig. 6
Fig. 6
Fig. 6Fig. 6
).
.
Trace A (5V/div.)
Inputs Board CheckInputs Board Check
Inputs Board Check
Inputs Board CheckInputs Board Check
➭ These procedures are intended for one channel at a time, repeat these
operations for the other channel.
SETUP:SETUP:
➭
SETUP:
SETUP:SETUP:
Connect the CH1 probe to amplifier input of the channel under test and
Trace B (2V/div.)
Solder the pins A-B of J16: the CH2 trace becomes continuous.
Increase the generator level for the max. displacement of the CH2 trace
toward the centre of the screen
Fig 7 Trace b
.
Wait until the temperature reaches 88°C, then turn clockwise the R62
trimmer to activate the SOA control (that is displayed by CH1 trace when
its peak voltage decrease
Fig 7 Trace A
), after some seconds, the channel goes in PROTECT mode.
Set the CH2 sensitivity at 5V/div. then, with its tip, check the voltage on
D19 cathode: it must be 14V or more.
Activate the fan and check its supply voltage: it must be 20V or more
set both at 500mV/div. 200mS/div.
Connect the CH2 probe to amplifier output of the channel under test and
set it at 10mV/div. 200mS/div.
Set the audio generator at 1KHz sinus. 775mV
RMS
(0dB).
Set the LEVEL potentiometers full clockwise.
The load resistor is disconnected.
CMRR ADJUSTMENTCMRR ADJUSTMENT
➭
CMRR ADJUSTMENT
CMRR ADJUSTMENTCMRR ADJUSTMENT
Temporarily disconnect pin 3 from pin 1 and short the pin 2 (positive
input) and pin 3 (negative input) of XLR input socket.
Adjust the trimmer R10 (channel A) or R21 (channel B) to obtain the
minimum output level.
(max. speed).
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