DBX 160-161 Calibration Procedure电路图.pdf

ISITIAL FACTORY TEST 6 ALIGN?!ENT PROCEDL7RE DBX MODELS lb0 AND 161 WITHOUT Ii47 & R39 (LATE 160 & 161) TEST EQUIWENT REQUIRED: QU_41T l7-YITEM 1Signal Oscillator 1Digital Multimeter 1Oscilloscope 1 . Wide Range db Deter 1Harmonic distortion meter 1 1 + 3 db meter (cal_ref. 1 volt) (optional) Resistor Substitution Box TYPE OR EQUIVALENT Kron-Hite 4200, Heath 1272 Dana 3300, B & K 282, Digitec 2110 Any (covering audio band) DBX SK-C-1026, HP 427 DBX SK-B-1070, Heath lM58, HP330, GR1500, CR1900 DBX SKC-1071 Any.k w 57. values, typically 10K to 470K NOTE:On model 160, tie It - IIterminals to Gnd,for normal testing. Revised 4-70-77 350325-03 RadioFans.CN 收音机爱 好者资料库 DBX MODELS 160 - 161 INITIAL TEST OUTLINE SEQUENCE OF STEPS: 1) Supply Trim 2) RMS Trim 3) VCA & RMS Symmetry 4) Level Calibration 5) Threshold Calibration 6) Gain Change & input zero calibration 7) Output Calibration 8) Input Tracking g) Compression Circuit Calibration 10) (R78) Correct Value Test 11) Clipping 12) Response 13) Signal Clamping (Model 160 only) 14) Noise 15) Seal Pots 16) Burn-in . 350025-03 RadioFans.CN 收音机爱 好者资料库 P-3 . 160/161 INITIAL PROCEDURE Before applying power to unit,check mechanical zero of meter. 1) 2) 274) 3) 4) 5) Supply Trim: Put resistance substitution box across R14 and measure DC voltage at (+) side of C7.Turn sub box until voltage is +15 volts + 50 MV (+14.950 to + 15.050). place. Solder appropriate resistor in Check (-) side of C8 to verify that it is -15 volts + 200 MV - (-14.800 to -15.200) RMS Trim: (205) Connect sub box across the two RMS trim pins, and measure the offset at the input pin of the RMS module.Trim the sub box until voltage is zero + 15 MV,and solder appropriate resistor in place. - (209) With input of 1.228 VRMS at 100 Hz,place sub box between + v and the trim pin on the RMS module.Drop input level to - 60 db and adjust sub box until a symmetrical waveform is observed on camp pin, insert value chosen in R36 spot (typ 8K to 75KR) VCA & RMS Symmetry: Set oscillator to 1.228 VRMS a) 100 Hz (Tune for peak on distortion meter) Set front panel compression knob to3 and output gain to +20.Turn threshold control counter clockwise from3 until external db meter reads 0 db.Turn trim pots R27 and R34 until distortion reads minimum. Level Calibration: Set oscillator to 1.228 VRMS a) 100Hz turn R63 until the voltage at the end of R79 (closest to the center of unit) is -.Oll VDC Threshold Calibration: Turn front panelThreshold Control until both leds are off.Loosen knob and position so that pointer indicates just past 1V and retighten. (When both leds are off the input signal is at threshold level.) (See fig. 1.)Step the oscillator up and down in 10 db steps verifying that the threshold level matches the input signal at successive calibration marks on the threshold dial. ,03 350025-03 RadioFans.CN 收音机爱 好者资料库 P4 6. GAIN CHANGE AND INPUT ZERO CALIBRATION 6.1 6.2 6.3 6.4 6.5 Set oscillator to 100 Hz at 1.228VRMS. Set THRESHOLD fully Cw. SetCOMPRESSION fully CCW. PlaceMETER switch toGAIN CHANGE and adjust R51 for precisely 0 on the DBX 160/161 meter. PlaceMETER switch to INPUT and adjust rear panel pot R62 for precisely 0 on the DBX 160/161 meter. Repeat steps 6.4 and 6.5.6.6 7. OUTPUT CALIBRATION 7.1 PlaceMBTER switch toOUTPUT and adjust precisely0 on the DBX 160/161 meter. If theOUTPUT GAINcontrol so that it points the OUTPUT GAIN control for necessary adjust the knob on precisely to0 on the front overlay at the same time that the DBX 160/161 meter reads precisely 0. 7.2 With the requirements of step 7.1 met,the external DB meter should read O+lDB. /7 8. INPUT TRACKING 8.1 Place METER switch toINPUT and step oscillator to -3ODB.Adjust R56 for a reading of precisely-30 on the DBX 160/161 meter. 9. COMPRESSION CIRCUIT CALIBRATION 9.1 9.2 9.3 9.4 9.5 9.6 Set THRBSHOLD fully CCW. Set COMPRESSION fully CW. Place METER switch to OUTPUT Step oscillator to -4ODB, and adjust the OUTPUT GAIN control for a convenient reading on the external DB meter.(E.G.-4ODB).Step the oscillator to +lODB.The change on the External DB meter must be less j-Y than 22DB. Adjust the OUTPUT GAIN control for a convenient reading on the DBX 160/161 meter.(E.G.-3ODB).Step the oscillator to -4ODB. The change on the DBX 160/161 meter should be less than +1DB.Trim R58 with RlO2 to obtain this reading.(150K Nominal) Set COMPRESSION to 4.Step oscillator to -3ODB. Adjust OUTPUT GAIN control for a convenient reading on the External DB meter. (E.G.-3ODB)Step oscillator to +lODB.The External DB meter should read-2ODB.Adjust R43 to obtain this reading.If necessary change R41 (7.5K) to 10K (Recheck if R43 is adjusted1 lo. (78) 10.1 10.2 10.3 10.4 CORRECT VALUB TEST Set THRESHOLD control fully CW. Apply 1OOHz at 1.228VRMS Set OUTPUT GAIN control for a reading of 0DB on the External +3DB meter. Vary theCOMPRESSION control from fully CCW to fully CW while watching the External DB meter.The change on the External DB meter must be less than +2DB. P5 11) Clipping: Step oscillator to + 1Odb and rotate compression control fully CCW.Turn output gain up until clipping is observed on the scope.Clipping should be clean and should occur well after + 20 dbm output for 160 and at +18 dbm for 161. 12) Response: Vary the frequency of the oscillator with Odb output, and verify that the output of the unit is constant + 1 db from 30 hz to 20 KHZ. 13) Signal Clamping (Model 160 only) For 160s turn power on and off,observing scope to check that the output does not contain a transient larger than the signal.After power is switched on the output should climb to normal, smoothly, in about a second. 14) Noise: Short input terminals and observe noise output of unit.With covers on, noise should read less than -80 dbm. 15) Seal pots with wax (all except R62). 16) Burn-in: Place in burn-in rack with appropriate power applied.(120 or 240 volts).