Dynacord DPA-4245 Service manual

SERVICE MANUAL

DPA 4245 / DPA 4260 POWER AMPLIFIER

MEASUREMENT SPECIFICATIONS: DPA power amplifiers complete appliance

Names of the individual printed board assemblies and their corresponding EDP numbers:

EDP numbers of the main boards

DPA 4245 DPA 4260

84 188 84 189

Board section Index

Main PCB 1

Supply PCB 4

LED PCB 3

Input-PCB (index 1) and Output-PCB (Index 2) are located on the printed board assembly 81340.

Measuring conditions, unless differently specified:

- measuring tolerance: X = 1.5dB

- measuring frequency: f = 1kHz

- all stated levels refer to: U = 775mV (0dBu)

- level controls are set to their clockwise margin:

- XLR connector pin-assignment: PIN 1 = GROUND/SHIELD PIN 2 = + INPUT PIN 3 = - INPUT

- source impedance for the induction via the XLR-type connector: R(Q) = 50 ohms

- the AMPLIFIER PCB is provided with service connectors:

CNS1 CNS2 CNRC

PIN Assigned to PIN Assigned to PIN Assigned to

1 -Vcc 1 LIM A Switch 1 LIM Out A 2 BIAS +A 2 -15V 2 LIM Out B 3 BIAS -A 3 LIM B Switch 3 Standby via RC 4 FAN Voltage 4 +15V 4 Standby LED 5 +Vcc 5 AGND 5 -Vss 6 BIAS +B 6 Speaker Out A 6 +Vss 7 BIAS -B 7 Relay/Protect 7 n.c. 8 Temp Heatsink 8 Speaker Out B 8 n.c.

- Pin-assignment of the power amplifiers output connector:

PIN Function Channel

1 + pole of the 100V output and + pole of the 25V output 2 - pole of the 25V output and + pole of the 70V output 3 - pole of the 70V output and - pole of the 100V output B 4 + pole Direct Output 5 - pole Direct Output

6,7 not assigned -

8 - pole Direct Output

9 + pole Direct Output 10 - pole of the 70V output and - pole of the 100V output A 11 - pole of the 25V output and + pole of the 70V output 12 + pole of the 100V output and + pole of the 25V output

Pin-assignment of the Power Remote connector: PIN 1 control voltage -

PIN 2 control voltage +

Nominal load impedances

100V output 70V output 25V output DPA 4245 DPA 4260

1. Operation voltage: U(B) = 230V / 50Hz ... 60Hz

2. Deviation limit of the operation voltage: -30% .... +10%

3. Power consumption (both channels driven via the 100V output, f = 1kHz)

idling condition power consumption 30-60W 40-80W nominal power consumption (nominal load) 1580W 1950W standard power consumption (nominal load) 470W 620W maximum power consumption (nominal load) 1680W 2180W power consumption at 1/8 of the maximum output capacity 600W 870W

4. Settings

4.1. IDLING CURRENT ADJUSTMENT

28,5ΩΩ 14ΩΩ 1,8ΩΩ

20ΩΩ 9,8ΩΩ 1,25ΩΩ

DPA 4245 DPA 4260

Connect the DC-volt meter at the BIAS measuring points (refer to service connectors) and adjust the idling current via the trim potentiometer VR101/VR301 (located on the Main PCB). Adjust both channels of the power amplifier A&B to U(DC) = 7.5mV. Adjusting the idling current has to be performed at normal room temperature. In case the power amplifier had previously been operated, it has to be given several hours to regain its normal temperature.

4.2. VCA - OFFSET

Rhythmically open and short-circuit CNS2.1 and CNS2.2 for channel A as well as CNS2.3 and CNS2.2 for channel B. The switches are located on the Main PCB. Using VR100 or VR300 respectively to adjust the power amplifier's Direct Output to its minimum offset (with oscilloscope to minimal peak value or to the audible minimal volume of the interfering pulse).

5. Functioning test

5.1. OUTPUT - offset voltage DC-voltage measuring at the Direct Output A/B with U(DC) 10mV.

5.2. LIMITER

5.2.1. Voltage limiter

Both channels separately driven without load via the Direct Output with a 1 kHz signal up to U(A) = 38V. Increase the input voltage by 10 dB. The LIMITER LED lights and the output voltage ascents by approx. 1.5 dB or 2.5 dB respectively to approx. 44V or 52V, respectively. The distortion rate of the limited signal should not ascent above 0.8%.

5.2.2. Distortion limiter Both channels separately driven via the Direct Output at 2Ω with a 1 kHz signal up to U(A) = 20V or U(A) =

25V, respectively. Increase the input voltage by 5 dB. The LIMITER LED lights and the output voltage ascents by approx. 1.5dB to approx. 25V or 29V respectively and it is slightly clipping. The distortion rate of the limited signal is approx. THD = 2 ... 3%. Further increasing the input signal by +10dB should not result in a remarkably higher clipping of the output signal.

5.2.3. Attack- and release times

separately testing the power amplifier channels is mandatory: Test has to be performed at the Direct Output

without load.

1.) Drive the power amplifier's input with a burst signal (f = 1kHz, 10 cycles, rate : 3 sec.) and U(E) = +10dBu.

2.) Monitor the output signal via oscilloscope. After 1 - 2 signal periods, the limiter has reduced the major distortion to a minor residual distortion (THD ≤ 1%)

attack time: approx. 2 ms release time: approx. 130 ms

5.3 POWER-ON DELAY

Feed the test signal to the power amplifier input. Switch the power amplifier ON using the "Power On" switch. Approximately 2 seconds after pressing the "Power On" switch, the signal is present at the output.

5.4 POWER REMOTE

Switch the power of the appliance OFF. Feed a control voltage of +24V to the Power Remote input. The power amplifier has to start operation and after disconnecting the control voltage has to go off again.

5.5 FAN CONTROL

Upon powering-on the power amplifier, the fans will run for approximately 2 seconds and stop when the power amplifier has re-gained its "normal" temperature. In idling condition (power-on, no signal present) the fans are switched between the SLOW and OFF mode, depending on the heat sink's temperature. Connecting the CNS1.8 via a 5kΩ resistor to +15V lets the fans run in SLOW mode. A FAN VOLTAGE of 16.8V DC can be measured between pin CNS2.4 and pin CNS1.4. When disconnecting CN5, the fans will run in FAST mode. A FAN VOLTAGE of 28V DC is measured between pin CNS2.4 and pin CNS1.4.

5.6 SOAR-PROTECTION TEST Channels separately driven up to 0dB via the Direct-Output, terminated with 4Ω. Parallel connect an 1Ω resistor.

The protection circuit reacts and tries continuously to re-start! The protect-LED lights.

5.7 SHORT-CIRCUIT CURRENT-LIMITING TEST

separately testing the power amplifier channels without load is mandatory:

- drive the channel with a burst signal (f = 1kHz, 1-3 cycles, rate ≈ 1 sec.), at the Direct Output with

U(E) = 0dBu.

- connect a load resistor of 1Ω.

- the short-circuit current-limiter limits the output voltage at the load resistor symmetrically (monitor via oscilloscope!) to a peak voltage value of 15V or 20V respectively (approx. 15A or 20A respectively maximum peak output current).

5.8 DC-voltage and HF-Protection Circuit

- Testing the protection circuitry against the occurrence of DC-voltage and HF at the output is only possible directly via the Main PCB when it is not installed in the appliance.

5.9 INDICATORS TEST

Feed a 1kHz sine signal while slowly increasing the level. At approx. -30dBu the SIGNAL LEDs will light and at approx. +1.5dBu the Limit LED will light.

6. Level CHANNEL A B

6.1. VOLTAGE AMPLIFICATION

Appliance Input U(E) Measuring point vU U(A) Load Frequency

DPA 4245 CH. A/B 0dBu Direct Out A/B 33.8dBu 37.8V DPA 4245 CH. A/B 0dBu 100V Output 42.2dBu 99.2V DPA 4245 CH. A/B 0dBu 70V Output 39.3dBu 71.6V

4Ω

28.5Ω 14Ω

1kHz 1kHz

1kHz DPA 4245 CH. A/B 0dBu 25V Output 30.2dBu 25.1V 1.8V 1kHz DPA 4245 CH. A 0dBu BRIDGED OUT 39.8dBu 76V DPA 4260 CH. A/B 0dBu Direct Out A/B 34.9dBu 43V DPA 4260 CH. A/B 0dBu 100V Output 41.8dBu 95.2V DPA 4260 CH. A/B 0dBu 70V Output 39dBu 68.8V DPA 4260 CH. A/B 0dBu 25V Output 29.8dBu 24V DPA 4260 CH. A 0dBu BRIDGED OUT 41dBu 87.3V

8Ω 4Ω

20Ω

9.8Ω

1.25Ω 8Ω

1kHz 1kHz 1kHz 1kHz 1kHz 1kHz

6.2. MAXIMUM INPUT LEVEL: U(E) = +21dBu

7. GROUND LIFT switch

The circuit ground (at the input or the output connector) is measured versus the common ground of the enclosure (contact at the ground terminal, located on the rear panel - or common ground of the mains cord). without input transformer GROUNDED : R = 0 Ω with input transformer GROUNDED : R = 0Ω

NOT GROUNDED: R = 5 Ω NOT GROUNDED: R→∞

8. Amplitude - Non-Linearities

- MBW = 80kHz

- all channels terminated with nominal load at nominal power, Direct Output at 8Ω or at 4Ω respectively, at

nominal power

Measurement DPA 4245 DPA 4260 Remarks

100V 70V 25V Direct 100V 70V 25V Direct THD+N IMD-SMPTE DIM 30

<0.1% <0.2% <0.3% <0.05% <0.1% <0.2% <0.3% <0.05% <0.1% <0.3% <0.5% <0.08% <0.2% <0.3% <0.5% <0.08% <0.2% <0.2% <0.2% <0.03% <0.2% <0.3% <0.3% <0.03%

1kHz

60Hz, 7kHz

3.15kHz, 15kHz

9. Frequency Response

The frequency response is linear. (mind the border frequencies)

fU -1dB fO -1dB fU -3dB fO -3dB

100V Output 60Hz 17kHz 45Hz 26kHz

70V Output 60Hz 17kHz 45Hz 26kHz 25V Output 60Hz 12kHz 45Hz 22kHz

Direct Output 60Hz 22kHz 45Hz 30kHz

10. Insert Attenuation

Drive the power amplifier in idling condition via the transformer outputs up to the nominal output voltage. Connect the nominal load and measure the level changes.

DPA 4245 DPA 4260

100V Output

70V Output 25V Output

0,7 dB 0,7 dB 0,8 dB 0,8 dB 1,1 dB 1,1 dB

11. Crosstalk

It is necessary to align the output transformers when testing the crosstalk. Therefore, turn the transformer outputs by 90° to each other and both by 45° to the rear panel. Terminate the 100V-outputs with nominal load and feed a 1kHz signal with -10dBu to the B-channel. Measure the crosstalk at the 100V output of the A-channel using a selective band pass filter and suitable measuring equipment. Turn the upper transformer for minimal reading. Apply a 1kHz signal with -10dBu at the A-channel and measure the crosstalk at the B-channel. Crosstalk attenuation on both channels has to at least ≥ 80dB .

12. Noise interference

- U(F) = external voltage un-weighted with B = 22 Hz … 22 kHz, effective value (IEC 268-1)

- U(G) = noise voltage, frequency-weighting filter according to CCIR-468-3, quasi peak weighted (IEC 268-1)

- U(A) = interference voltage A-weighted, dB(A), effective value (IEC 268-1)

- Signal-to-noise ratio referenced to the maximum output voltage at nominal load, A-weighted

- All inputs have to be terminated with 50Ω each; during the noise interference measurement, the outputs have to be without load

Power amplifier Output U(F)

dBu LEVEL control up DPA 4245, 4260 100V -55 -45 -57 -102 100 DPA 4245, 4260 70V -58 -47 -60 -102 100 DPA 4245, 4260 25V -68 -56 -70 -102 100 DPA 4245, 4260 Direct -64 -52 -66 -102 100 LEVEL control down DPA 4245, 4260 100V -57 -47 -59 - DPA 4245, 4260 70V -59 -50 -61 - DPA 4245, 4260 25V -70 -58 -72 - DPA 4245, 4260 Direct -66 -54 -68 - -

13. Settings when shipped

BRIDGED MODE switch set to NORMAL. INPUT ROUTING switch set to DUAL/STEREO. LEVEL control all the way right.

14. Dimensions and Weight

Power amplifier Weight Dimensions in mm

DPA 4245 20.5kg 483 x 132.5 x 385.5 DPA 4260 22.5kg 483 x 132.5 x 385.5

U(G)

dBu

U(A)

dBu

IN(A)

dBu

S/N-R.

+ 20 hidden pages

Dynacord DPA-4245 Service manual

Specifications and Main Features

Frequently Asked Questions

User Manual