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Model 3BX III Service Manual

 

– 25 –   

MODEL 3BX III MAIN ASSEMBLY 

REFERENCE 

DESIGNATION 

DESCRIPTION 

PRODUCT CODE 

DBX PM 

QTY 

1-A ESCUTCHEON 

510ME9SEAA024 

290693 

1-B BUTTON/LED 

GUIDE 

510VF132SBOO4 

210213 

2, 3, 4 

VR KNOB ASSEMBLY 

510AVKNOB*175 

380211 

B15 

PAN HEAD RIVET M3 x 4.5 QCK NYLON-B 

510BRP3045QNB 

310467 

B14 

THIN HEAD RIVET M2.4 x 5.5 STD AL 

510BRU2455XAJ 

310648 

B2 

BIND HEAD SCREW(+) M3 x 12 S-ZMC 

510BSPB3012NZ 

310649 

B1 

BIND HEAD SCREW(+) M4 x 10 S-BLK 

510BSPB401ONB 

310650 

B4-6 

BIND T.T. SCREW(+) M3 x 5 S-BLK S-T 

510BTPBOO5ONB 

310651 

B7-12 

BIND T.T. SCREW(+) M3 x 5 S-ZMC S-T 

510BTP83005TZ 

310437 

13 

B3 

FLAT T.T. SCREW(+) M3 x 5 S-ZMC S-T 

510BTPS3005TZ 

310653 

B16 

FLAT L WASHER M3 x 7 x 0.5T S-NI 

510BWM30705SN 

310654 

B17 

IT LOCK WASHER M3 x 6.5 x 0.5T S-BLK 

510BWU30655SB 

310655 

B13 

IT WASHER M4 x 8.5 x 0.5T S-BLK 

510BWU40855SB 

310656 

6

REAR PANEL 

510MB951SE010 

290695 

17 

BRACKET SW A 

51OML464SLOOI 

290696 

16 

BRACKET SWITCH 2255095 RB0010-011 

51OML544SDO04 

290554 

19 COVER 

SWITCH 

510MS625AA002 

290698 

5

CHASSIS 510MU984SLOO1 

290699 

 

8

COVER 510MU985SM001 

290700 

20 

SERIAL NUMBER PLATE 

510MVSSX10**1 

290701 

22 

FOOT BASE ONLY 

51ONBR9227577 

380217 

22 

FOOT CUSHION ONLY 

51ONBR2675132 

380217 

12 

VOLUME CONTROL BUSHING 

510VF177DBOO1 

210219 

15 

POWER SWITCH BUTTON EXTENDER 

510VK321SBOOI 

210097 

11 PUSH 

KNOB 

510VN220SH004 

210221 

27 SPONGE 

SPACER 

510VS336RF001 

210222 

25 SHEET 

TRANS 

510VS667X8001 

310664 

B18 WASHER 

A4 

510VS704VF002 

310659 

18 

LED PCB HOLDER 

510VS74ISBOO1 

210230 

AC01 

AC CORD ASSEMBLY (UL/CSA AND PX UNITS ONLY) 

510ACAC029ULA 

320087 

AC01 

AC CORD ASSEMBLY (EUROPEAN UNITS ONLY) 

510ACAC171EEA 

320133 

col 

CAPACITOR CERAMIC 1000pF RAD AC 125V OR 4700pF 
UL/CSA 

51OCKDU102KBM 121539  1 

LD01, LD04 

LED LN222RP RED 

510QLBLN222RN 

140202 

LD02, 03, 05, 06 

LED LN322GP GREEN 

510QLBLN322GN 

140204 

SW1 

POWER SWITCH (UL/CSA AND PX UNITS ONLY) 

510SPO1AAW02A 

250072 

sol 

VOLTAGE SELECTOR SWITCH HSW0573-01-310 (UL/CSA AND 

PX UNITS ONLY) 

51OSS010226AJ 250096  1 

PT1 

POWER TRANSFORMER (110/220V, UL/CSA AND PX UNITS 

ONLY) 

510TPL41U001K 230035  1 

ACB1 

POWER CORD BUSHING SR3P-4 (UL/CSA AND PX UNITS 

ONLY) 

510VM27ONBOO1 310403  1 

ACB1 

POWER CORD BUSHING (EUROPEAN UNITS ONLY) 

510VM27ONBOO4 

310469 

ZZ1 

SOLDERLESS CONNECTOR CE-230 (UL/CSA AND PX UNITS 

ONLY) 

510ZZZ0000154 280089  1 

PT1 

POWER TRANSFORMER (220V EUROPEAN UNITS ONLY) 

510TPL415001K 

230036 

SW1 

POWER SWITCH (EUROPEAN UNITS ONLY) 

510SPO1AASI7N 

250073 

POWER SWITCH COVER (EUROPEAN UNITS ONLY) 

510VB443SBOOI 

210091 

RACK MOUNT ADAPTOR 

51OML543AA003 

290703 

2

 

Содержание 3BX III

Страница 1: ...Impact Restoration SERVICE MANUAL All dbx products are manufactured under patents in the US and abroad and on all dbx circuit designs dbx holds copyright in one or more of the following years 1979 85...

Страница 2: ......

Страница 3: ...CV Path 7 Mid Band CV Path 7 LED DISPLAYS 7 POWER SUPPLY and MUTE GENERATOR 8 ALIGNMENT PROCEDURE 9 1 INSTRUMENTS REQUIRED 9 2 INSPECTION and WARMUP 9 3 POWER SUPPLY TESTS 9 4 CONTROL CIRCUITRY TESTS...

Страница 4: ...All data are for 20 Hz 20 kHz unless otherwise specified line inputs are driven by a source impedance of 1 k ohms and outputs are loaded by 10 k ohms in parallel with 1000 pF all voltages are rms root...

Страница 5: ...ates the signal path or detector path the detector section is common to both channels so 700 components ending in a number are in this area while those ending in L or R are in the signal path The 800...

Страница 6: ...gnment section allow for a small adjustment When pin 3 is positive the gain in dB is negative less than unity when pin 3 is negative the gain in dB is positive greater than unity Also under ideal cond...

Страница 7: ...oltages can then be processed and used to control the gain of the VCAs in the 3BX III to accomplish its two purposes Choosing the correct time constants for the rms detectors in the first place is cri...

Страница 8: ...nput signals the rms IC output is positive and negative for smaller input signals it varies by 6 mV for each decibel of input level change The time constant of the rms detector is dependent on the cap...

Страница 9: ...sion control When TP14 is negative the gain will be positive or 0 The wiper of the expansion control connects to the positive input of a summer stage 2 2 U719 whose output is sent on to the VCA TP14 a...

Страница 10: ...V div 4 a 2 4 b 2 4 c 2 Top Low band rms buffer output U710 pin 7 TP10 1 V div Top Mid band rms buffer output U711 pin 7 TP12 1 V div Top High band rms buffer output U722 pin 7 TP14 1 V div Bottom Lo...

Страница 11: ...in 1 2 U718 and then sent to the low band VCAs Trim pots VR717 and VR718 are provided to set the VCA gains precisely Mid Band CV Path This path also closely resembles the high band except for differe...

Страница 12: ...h An open in a comparator output will cause its LED to light as soon as the one above it is lit a short in a comparator output will prevent any LEDs from lighting below that comparator POWER SUPPLY an...

Страница 13: ...properly installed 2 2 Confirm that the voltage selector switch is in the proper position 2 3 Connect the unit to a source of rated AC voltage turn it on and let it warm up for 10 minutes 3 POWER SUPP...

Страница 14: ...best rms symmetry as shown in Fig 7a 4 1 4 Reset the oscillator to 100 Hz 10 dBV 3 16 V 4 1 5 Also connect a digital voltmeter to TP10 4 1 6 Adjust VR705 for 0 00 Vdc 10 mV Verify that no more than on...

Страница 15: ...Level TP12 Voltage Tolerance 15 dBV 000 mV dc 10 mV 5 dBV 541 mV dc 50 mV 5 dBV 1080 mV dc 100 mV 15 dBV 1620 mV dc 150 mV 4 3 High band rms calibration 4 3 1 Set the controls as in 4 1 1 4 3 2 Conne...

Страница 16: ...VR723 the impact release rate control on the rear panel 4 5 2 Set VR723 so that the voltage measures 6 75 Vdc 5 VCA SYMMETRY ADJUSTMENTS 5 1 VCA Symmetry Adjustment Low Band Left Channel 5 1 1 Set the...

Страница 17: ...Connect the sine wave oscillator to the left and right inputs of the 3BX III 6 3 Left Channel Adjustment 6 3 1 Set the oscillator for 100 Hz at 0 dBV 1 V rms 0 1 dB 6 3 2 Connect the left channel outp...

Страница 18: ...burst oscillator 7 1 4 Low Band Test 7 1 4 1 Set the oscillator to 100 Hz at 0 dBV 1 V rms and the tone burst oscillator to produce approximately an 80 ms burst 8 cycles followed by approximately 500...

Страница 19: ...5 3 Observe that the Impact display lights at least 10 out of the 12 LEDs 7 1 6 High Band Test 7 1 6 1 Set the oscillator to 10 kHz at 0 dBV and the tone burst oscillator to produce approximately a 3...

Страница 20: ...r 1 V div and 50 ms div 7 2 3 2 Observe the output on the scope Verify that the shape is substantially as shown in Fig 10a confirm for the other channel Figure 10a 7 2 3 3 Observe that the Low Band di...

Страница 21: ...AC voltmeter Figure 10b 7 2 4 3 Observe that the mid band display lights at least to the 4th red LED during the burst and returns to the 1st red LED between bursts 7 2 5 High Band Test 7 2 5 1 Set the...

Страница 22: ...ion Minimum Impact Restoration Minimum Transition Level Mid Point Pre Post Pre Source Tape Source Bypass Out not set 7 4 2 Connect the sine wave oscillator to the unit s left and right inputs 7 4 3 Co...

Страница 23: ...f the rms responding AC voltmeter 7 5 4 Verify that the noise level is less than 85 dBV unweighted or 90 dBV A weighted 0 dBV is 1 V rms 7 6 Muting Check 7 6 1 Set the unit as in 7 4 1 7 6 2 Connect t...

Страница 24: ...776R ELECT CAP 4 7uF RAD NP 25V 20 510CEVE4R7RAN 127161 2 C710 15 721 722 730 732 739 740 742 747 751 753 755 757 760 767 769 770 775 807 ELECT CAP 1uF 50V 20 510CEVGOIOALX 127084 34 C706L 706R 707L 7...

Страница 25: ...2162 1 QL01 LO8 PNP TRANSISTOR 2SA1020 Y SIOQTA102OXAT 142171 8 Q701 703 NPN TRANSISTOR 2SC1815 Y 510QTC1815XAT 142172 3 Q801 802 PET TRANSISTOR 2SKI70 510QTX0170XAT 142173 2 R746 760 774 RESISTOR CAR...

Страница 26: ...5 51ORD25PJ221X 054221 4 R807 RESISTOR CARBON FILM 1 4W 2 2K ohm 5 51ORD25PJ222X 054222 1 R7F3 737 749 764 RESISTOR CARBON FILE 1 4W 22K ohm 5 SIORD25PJ223X 054223 4 R7E8 RESISTOR CARBON FILM 1 4W 22...

Страница 27: ...0K ohm 5 51ORD2SPJ754X 054754 3 R741 753 767 RESISTOR CARBON FILM 1 4W 82K ohm 5 SIORD25PJ823X 054823 3 R743 755 769 RESISTOR CARBON FILM 1 4W 9 1K ohm 5 SIORD25PJ912X 054912 3 R742 754 768 RESISTOR M...

Страница 28: ...R SHIELDED WIRE 2 CONDUCTOR 51OWWX845JXJJ 320121 A R CN704 LED WIRING JUNCTION JACK 8 PIN SIOYJFOBS028Z 280222 1 CN701 703 LED WIRING JUNCTION JACK 10 PIN 510YJPIOS044Z 280223 3 CN705 706 LED WIRING J...

Страница 29: ...217 4 22 FOOT CUSHION ONLY 51ONBR2675132 380217 4 12 VOLUME CONTROL BUSHING 510VF177DBOO1 210219 3 15 POWER SWITCH BUTTON EXTENDER 510VK321SBOOI 210097 1 11 PUSH KNOB 510VN220SH004 210221 6 27 SPONGE...

Страница 30: ...Model 3BX III Service Manual 26 SCHEMATIC...

Страница 31: ...Model 3BX III Service Manual 27 CIRCUIT BOARD COMPONENT SIDE TOP...

Страница 32: ...Model 3BX III Service Manual 28 CIRCUIT BOARD NON COMPONENT SIDE BOTTOM...

Страница 33: ...Model 3BX III Service Manual 29 LED SCHEMATIC PCB PINOUTS...

Страница 34: ...Model 3BX III Service Manual 30 MECHANICAL ASSEMBLY EXPLODED VIEW...

Страница 35: ...re not to lose the plastic grommet Audible hum If the unit produces audible hum in the output it s likely that some of the power supply filter capacitors have dried out or leaked It is recommended you...

Страница 36: ...Model 3BX III Service Manual 32 NOTES...

Страница 37: ...3853C 600307 Printed in USA...

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