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PROCON1250 - Test procedures andPROCON1250 - Test procedures and
PROCON1250 - Test procedures andPROCON1250 - Test procedures and
PROCON1250 - Test procedures and
adjustmentsadjustments
adjustmentsadjustments
adjustments
PRECAUTIONPRECAUTION
PRECAUTIONPRECAUTION
PRECAUTION
• To prevent short circuit during any test, the oscilloscope must
be 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.
• 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 supply capacitors. If
your measurement on any of the caps is greater than 10Vdc,
connect a 100E 90W resistor across the applicable caps to
discharge them for your safety. Remember to remove the
discharge resistor immediately after discharging caps. Do not
power up the amplifier with the discharge resistor connected.
• Do not check the amplifier with the speakers connected use the
appropriate load resistors only.
• BE CAREFUL increasing the Variac you must not exceed the
nominal mains voltage plus its tolerance (see specifications) any
upper voltage can be cause of damage.
VISUAL CHECKVISUAL CHECK
VISUAL CHECKVISUAL CHECK
VISUAL CHECK
• Use compressed air to clear dust in the amplifier chassis.
• Before proceed to supply the amplifier check visually the
internal assembly, if appears an evident damage find the most
possible reasons that cause it.
• Check the wiring cables for possible interruptions or shorts.
• If the damage has burnt a printed circuit board don’t try to
repair it, replace with a new one.
TESTING GEARTESTING GEAR
TESTING GEARTESTING GEAR
TESTING GEAR
• Audio Generator
• Dual Trace Oscilloscope
• Digital Multimeter
• 4E 700W, 8E 450W, 100E 90W resistors
• Variac
• Digital Thermometer (not indispensable)
SETUPSETUP
SETUPSETUP
SETUP
• Connect the Variac between the Mains and the amplifier and
set it at zero voltage.
• Turn full counter-clockwise the LEVEL potentiometers.
• Connect the audio generator to the channel inputs and set it to
1KHz 775mVrms (0dBm) sinusoidal signal.
• Connect the two scope traces to the amplifier outputs, before
the relay, and set them in DC at 20V/div. 2mS/div.
SUPPLY CHECKSUPPLY CHECK
SUPPLY CHECKSUPPLY CHECK
SUPPLY CHECK
• Verify with the Multimeter the insulation between the heatsinks
and all transistor collectors mounted on them; placing the
multimeter tips between the screw heads and the collector pins
you can exclude an erroneus reading due to the insulation of the
heatsink anodization.
• Verify with the Multimeter the NTC (RT1) and R1 paralleled
resistor value, it must be about 7KE (at 25°c).
• Turn on the Amplifier.
• Remove the transformer secondary fuses, set the Variac to the
nominal mains voltage, check with the Multimeter the AC supply
voltages:
F1-F2 = 28±2Vac.
F3-gnd and F4-gnd = 69±7Vac.
• Re-set the Variac at zero voltage, turn off the amplifier and put
the fuses back on its holders.
• Set up the Variac slowly monitoring the oscilloscope screen, it
should display no signal; if you notice a DC voltage or a
protectiontrips check the amplifierassuggested in the ADVICES.
• As soon as the +12VF supply circuit reaches its nominal value,
all cooling fans run at their minimum and the speaker output
relais (J201-202) switch.
• When the Variac ac voltage reaches the nominal voltage verify
the DC supplies as follow:
+VCC = +93±7Vdc
-VCC = -93±7Vdc
U201 pin 8 = +12±0.5Vdc
U201 pin 4 = -12±0.5Vdc
U202 pin 3 = +12±0.5Vdc
• If one or more voltages don’t correspond, check the rectifiers,
capacitors and transformers disconnecting them from circuitry.
CHANNEL CHECKCHANNEL CHECK
CHANNEL CHECKCHANNEL CHECK
CHANNEL CHECK
• Be sure you have disconnected the load resistor.
• Increasing the input
signal also the output
signal raise accordingly,
it must be symmetrical
withoutvisible distortion
or oscillation as shown in
figure (note: the figure
is representative don`t
refer to the levels dis-
played). If there is a dis-
tortion read the section
ADVICES.
• When the input signal
exceeds -23dBm (10Vpp
on output) the SIGNAL
led lights and the fans
turn at their maximum
speed.
• Firstly you must check the channel without load, afterwards
you must repeat the check with the loads attached, the following
table reports the approx. maximum level obtainable with this
amp:
out level in level
no load 180Vpp +2.0dBm
1CH 8E 160Vpp +1.0dBm
1CH 4E 144Vpp +0.3dBm
2CH 8E 148Vpp +0.6dBm
2CH 4E 130Vpp -0.5dBm
CLIP LED ADJUSTMENTCLIP LED ADJUSTMENT
CLIP LED ADJUSTMENTCLIP LED ADJUSTMENT
CLIP LED ADJUSTMENT
• Check if the clip led lights at -6/-5dBm on input (~84Vpp on
output), if necessary adjust the trimmers W301/2 on display
board.
OFFSET ADJUSTMENTOFFSET ADJUSTMENT
OFFSET ADJUSTMENTOFFSET ADJUSTMENT
OFFSET ADJUSTMENT
• Set the input level at minimum (no signal), the output dc offset
voltage must be within ±20mV, if necessary adjust the VR101
trimmer (for each channel) to be within this threshold.
BIAS ADJUSTMENTBIAS ADJUSTMENT
BIAS ADJUSTMENTBIAS ADJUSTMENT
BIAS ADJUSTMENT
• No bias adjustment is necessary for this amplifier circuitry; in
any case the amplifier has the possibility to adjust it if necessary.
To check properly the bias proceed as follows:
• Using a sinusoidal signal (1KHz or more) and the 4E load
attached, wait till the heatsink temperature reaches about 60°c.
• Turn down the signal at the smallest intensity you can read on
your oscilloscope trace connected at the amplifier output.
• Zoom in the crossing region using the amplitude, timebase and
trigger controls of your oscilloscope. If you see a distortion, try
to eliminate it adjusting the VR102 trimmer.
• Finally, set the input level at minimum and verify with the
multimeter attached across an emitter resistance (p.e. R132)
that the dc voltage doesn`t exceed 10mV.
ADVICESADVICES
ADVICESADVICES
ADVICES
• If you have determinate that the problem is a short on a rail,
you must check the output transistors.
• To determine which transistor devices are bad, use a soldering
iron to lift one leg of each emitter pin and measure the resistance
across emitter and collector of each device. Unsolder and lift one
leg of each base pin and check the base-collector resistance.
Replace any device that measure as a short.
• If all the transistors are OK, unsolder and lift one leg of each
diode and check them.
• Check the circuit board for open foil traces.
• Use the Multimeter to check the resistors, particularly the base
and emitter resistors of damaged transistor.
• If the input sinewave appears to be distorted during the
negative cycle, you can assume that the problem is located
somewhere in the circuitry of the positive rail.
• If the positive cycle appears distorted, you can assume that
the problem is in the circuitry of the negative rail.
• The dc voltages printed on the schematics are measured with
the amplifier in steady state without input signal and nominal
mains voltage supply, it can be useful to localize a damage.
PROCON1500 - Test procedures andPROCON1500 - Test procedures and
PROCON1500 - Test procedures andPROCON1500 - Test procedures and
PROCON1500 - Test procedures and
adjustmentsadjustments
adjustmentsadjustments
adjustments
PRECAUTIONPRECAUTION
PRECAUTIONPRECAUTION
PRECAUTION
• To prevent short circuit during any test, the oscilloscope must
be 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.
• 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 supply capacitors. If
your measurement on any of the caps is greater than 10Vdc,
connect a 100E 100W resistor across the applicable caps to
discharge them for your safety. Remember to remove the
discharge resistor immediately after discharging caps. Do not
power up the amplifier with the discharge resistor connected.
• Do not check the amplifier with the speakers connected use the
appropriate load resistors only.
• BE CAREFUL increasing the Variac you must not exceed the
nominal mains voltage plus its tolerance (see specifications) any
upper voltage can be cause of damage.
VISUAL CHECKVISUAL CHECK
VISUAL CHECKVISUAL CHECK
VISUAL CHECK
• Use compressed air to clear dust in the amplifier chassis.
• Before proceed to supply the amplifier check visually the
internal assembly, if appears an evident damage find the most
possible reasons that cause it.
• Check the wiring cables for possible interruptions or shorts.
• If the damage has burnt a printed circuit board don’t try to
repair it, replace with a new one.
TESTING GEARTESTING GEAR
TESTING GEARTESTING GEAR
TESTING GEAR
• Audio Generator
• Dual Trace Oscilloscope
• Digital Multimeter
• 4E 800W, 8E 500W, 100E 100W resistors
• Variac
• Digital Thermometer (not indispensable)
SETUPSETUP
SETUPSETUP
SETUP
• Connect the Variac between the Mains and the amplifier and
set it at zero voltage.
• Turn full counter-clockwise the LEVEL potentiometers.
• Connect the audio generator to the channel inputs and set it to
1KHz 775mVrms (0dBm) sinusoidal signal.
• Connect the two scope traces to the amplifier outputs, before
the relay, and set them in DC at 20V/div. 2mS/div.
SUPPLY CHECKSUPPLY CHECK
SUPPLY CHECKSUPPLY CHECK
SUPPLY CHECK
• Verify with the Multimeter the insulation between the heatsinks
and all transistor collectors mounted on them; placing the
multimeter tips between the screw heads and the collector pins
you can exclude an erroneus reading due to the insulation of the
heatsink anodization.
• Verify with the Multimeter the NTC (RT1) and R1 paralleled
resistor value, it must be about 7KE (at 25°c).
• Turn on the Amplifier.
• Remove the transformer secondary fuses, set the Variac to the
nominal mains voltage, check with the Multimeter the AC supply
voltages:
F1-F2 = 28±2Vac.
F3-gnd and F4-gnd = 71±8Vac.
• Re-set the Variac at zero voltage, turn off the amplifier and put
the fuses back on its holders.
• Set up the Variac slowly monitoring the oscilloscope screen, it
should display no signal; if you notice a DC voltage or a
protectiontrips check the amplifierassuggested in the ADVICES.
• As soon as the +12VF supply circuit reaches its nominal value,
all cooling fans run at their minimum and the speaker output
relais (J201-202) switch.
• When the Variac ac voltage reaches the nominal voltage verify
the DC supplies as follow:
+VCC = +100±8Vdc
-VCC = -100±8Vdc
U201 pin 8 = +12±0.5Vdc
U201 pin 4 = -12±0.5Vdc
U202 pin 3 = +12±0.5Vdc
• If one or more voltages don’t correspond, check the rectifiers,
capacitors and transformers disconnecting them from circuitry.
CHANNEL CHECKCHANNEL CHECK
CHANNEL CHECKCHANNEL CHECK
CHANNEL CHECK
• Be sure you have disconnected the load resistor.
• Increasing the input
signal also the output
signal raise accordingly,
it must be symmetrical
withoutvisible distortion
or oscillation as shown in
figure (note: the figure
is representative don`t
refer to the levels dis-
played). If there is a dis-
tortion read the section
ADVICES.
• When the input signal
exceeds -24dBm (10Vpp
on output) the SIGNAL
led lights and the fans
turn at their maximum
speed.
• Firstly you must check the channel without load, afterwards
you must repeat the check with the loads attached, the following
table reports the approx. maximum level obtainable with this
amp:
out level in level
no load 190Vpp +1.8dBm
1CH 8E 170Vpp +0.8dBm
1CH 4E 158Vpp +0.2dBm
2CH 8E 159Vpp +0.3dBm
2CH 4E 142Vpp -0.8dBm
CLIP LED ADJUSTMENTCLIP LED ADJUSTMENT
CLIP LED ADJUSTMENTCLIP LED ADJUSTMENT
CLIP LED ADJUSTMENT
• Check if the clip led lights at -6/-5dBm on input (~88Vpp on
output), if necessary adjust the trimmers W301/2 on display
board.
OFFSET ADJUSTMENTOFFSET ADJUSTMENT
OFFSET ADJUSTMENTOFFSET ADJUSTMENT
OFFSET ADJUSTMENT
• Set the input level at minimum (no signal), the output dc offset
voltage must be within ±20mV, if necessary adjust the VR101
trimmer (for each channel) to be within this threshold.
BIAS ADJUSTMENTBIAS ADJUSTMENT
BIAS ADJUSTMENTBIAS ADJUSTMENT
BIAS ADJUSTMENT
• No bias adjustment is necessary for this amplifier circuitry; in
any case the amplifier has the possibility to adjust it if necessary.
To check properly the bias proceed as follows:
• Using a sinusoidal signal (1KHz or more) and the 4E load
attached, wait till the heatsink temperature reaches about 60°c.
• Turn down the signal at the smallest intensity you can read on
your oscilloscope trace connected at the amplifier output.
• Zoom in the crossing region using the amplitude, timebase and
trigger controls of your oscilloscope. If you see a distortion, try
to eliminate it adjusting the VR102 trimmer.
• Finally, set the input level at minimum and verify with the
multimeter attached across an emitter resistance (p.e. R132)
that the dc voltage doesn`t exceed 10mV.
ADVICESADVICES
ADVICESADVICES
ADVICES
• If you have determinate that the problem is a short on a rail,
you must check the output transistors.
• To determine which transistor devices are bad, use a soldering
iron to lift one leg of each emitter pin and measure the resistance
across emitter and collector of each device. Unsolder and lift one
leg of each base pin and check the base-collector resistance.
Replace any device that measure as a short.
• If all the transistors are OK, unsolder and lift one leg of each
diode and check them.
• Check the circuit board for open foil traces.
• Use the Multimeter to check the resistors, particularly the base
and emitter resistors of damaged transistor.
• If the input sinewave appears to be distorted during the
negative cycle, you can assume that the problem is located
somewhere in the circuitry of the positive rail.
• If the positive cycle appears distorted, you can assume that
the problem is in the circuitry of the negative rail.
• The dc voltages printed on the schematics are measured with
the amplifier in steady state without input signal and nominal
mains voltage supply, it can be useful to localize a damage.
