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Model 3BX III Service Manual

 

– 20 –   

MODEL 3BX III PRINTED CIRCUIT BOARD ASSEMBLY 

REFERENCE 

DESIGNATION 

DESCRIPTION 

PRODUCT CODE 

DBX P/N 

QTY. 

LED CONNECTOR CORD ASSEMBLY, M” LEADS 

510ACCNL31ULA 

310472 

POWER LED CONNECTOR CORD ASSEMBLY 

SIOACC9L7SULA 

320215 

CONNECTOR RED, ASSEMBLY 

510ACZZ243CFA 

320216 

HEX NUT M3 x N-P S-ZMC 

510BN11CL30NSZ 

310626 

PAN READ RIVET 43 x 4.5 QCK NYLON-B 

SIOBRP3045QNB 

310467 

PAN HEAD SCREW M3 x 8 S-ZMC 

510BSPP3008NZ 

310628 

CND WASHER M3 x 6 x .2T BS-NI 

510BWT30602BN 

310660 

C701L, 701R 

CERAMIC CAP. 100pF RAD DC 50V, 10% NPO OR S2L 

510CCGB101JOT 

121258 

C709L, 709R, 
777, 778 

CERAMIC CAP. 33pF RAD DC 50V, 10%, NPO 

51OCCGB330JOT 

121174 

CBOI-804 

ELECT CAP 470uF RAD 35V, +50/-10% 

SIOCKAF471ALX 

127490 

C719, 728, 

738, 805, 806, 
808 

ELECT CAP 10uF RAD 25V. +50/-10% 

510CEVE100ALX 

127203 

C720 

ELECT CAP 22uF RAD 25V, 10% (MAY BE NP) 

510CEVE220ALX 

127264 

C729 

ELECT CAP 3.3uF RAD 25V, 10% 

51OCEVE3R3ALX 

127100 

C776L, 776R 

ELECT CAP 4.7uF RAD NP, 25V, 20% 

510CEVE4R7RAN 

127161 

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, 707R 

ELECT CAP 1uF RAD NP 50V, 10% 

510CEVCO1ONAN 

127087 

C774 

ELECT CAP 1.5uF RAD 50V, 20% 

510CEVG1R5ZMN 

177088 

C717, 718, 
726, 727, 736, 

737 

CERAMIC CAP 1000pF 50V 10% Y5E 

51OCKGB102KBT 

121432 

C733, 735, 
745, 746, 752 

FILM CAP 1uF RAD 50V, 5% 

510CQVB104JTW 

123149 

C754, 758 

FILM CAP .047uF RAD 50V, 5% 

510CQV8473JTN 

123095 

C702L, 702R 

FILM CAP .068uF RAD 50V, 5% 

510CQV8683JTN 

123123 

C708L, 708R, 

716, 723, 725. 
731, 741, 768 

FILM CAP .33uF RAD, 50V, 5% 

510CQ48334JEH 

123213 

C734, 759 

FILM CAP .01uF RAD 50V, 5% 

510CQ8B103JTN 

123025 

C704L, 704R, 
705L, 705R, 

744 

FILM CAP 3300pF RAD 50V, 5% 

510CQ85332JTN 

123350 

C703L, 703R, 

724, 743 

FILM CAP .033uF RAD 50V, 5% 

SIOCQ8R333JTN 

123075 

C771 

FILM CAP 5600pF RAD 50V, 5% 

SIOCQ88682JTN 

123098 

HEAT SINK 2335389 R81071-004 

SIONS736ADOOI 

310629 

TERMINAL SIONW20155001 

310630 

20 

SHORT JUMPER 10 mm 

SIOMW4OICX006 

110085 

183 

BUSHING ASSEMBLY 2666116 TB-30012675136 R80010-019 

51OWBR2666116 

310679 

4 PR 

SIONIRR2675136  

 

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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