165 calibration procedure

8/2/2019 165 Calibration Procedure

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DBX 165 5-23-91Note: Adjustments should be made in this order. Make a visualinspection of the unit for mechanical and cosmetic flaws.

1. SETUPA. center all trimmers.B. Set STEREO COUPLER button out.Set AUTO button in.Set GAIN CHANGE button in.Set SYSTEM BYPASS button out.Set THRESHOLD (R60) to +10. cuJSet COMPRESSION (R141) to 1. CCwSet ATTACK (R82) to 400 dBjMSEC. u..",JSet RELEASE (R86) to 4K dBjSEC.CCLJJSet STOP LEVEL (R164) to +24.cWSet OUTPUT GAIN (R135) to O.O~~Note: Use 400Hz filter as needed.2. POWER SUPPLY VOLTAGE TESTA. Set the POWER button in. Verify 88 ohms between the bladesof theAC cord. Verify 0 ohms between the ground pin of the.AC cord and the chassis of the UUT. Verify infiniteresistance between either blade of the AC cord and theground pin.B. Set POWER switch in .Verify that the power LED is lit.Verify that the BELOW THRESHOLD (green) LED is lit, andthat the AUTO ATTACKjRELE;ASE LED is J.it. _/oC. Monitor the junction of R14 and c6.ff-'Adjust+15V .ADJ (R8) P

for 15.00VDC +j- 10mVDC. Monitor the junction of R15 andI4-~R19. Verify -15.00y~c (+j- 100mVDC). Monitor the collector(metal can) of Q~B../verify20.OOVDC (+j- 200mVDC). Monitorthe collector (metal can) of Q12:;:'X>Verify-20.00Vdc +j-400mVDC. Be sure to be nice to Mandy.D. Monitor the junction of R92 and the wiper of R93. Set R93(~-O)for -1.35VDC at this test point. (1;;"-0';3. INPUT GAIN AND CHECK CMRR CHECK ()~5-A. Apply 100Hz @ OdBu to the input of the UUT.B. Verify -ldBu at pin 6 of OA5 and -6dBu at pinC. Verify CMRR > 40dBu at pin 6 of OA5 and pin 1(j-X)4. RMS SYMl-iETRYADJUSTA .Apply 100Hz @ OdBu to the input of the UUT. Monitor pin 5 (7-1...,)of ~~through the Sound Tech with. the distortion outputdisplayed on the scope. Set the Sound Tech to dB VOLTS.(5-:5) Adjust _ . E 4 ! > until the waveform peaks are the same height.~ You should get a near perfect sine wave. Monitor pin 5 ofr . . . , . " r i ' " QAi and pin 5 of ~. '~A~~'B'"S~~!i~1EE"G~t~\ f } . ''_'""_'''j-.':i'"'."='''''j;;.;_,,,> ..~?'W> __' . ,.... ....- - . - . c : : "._=-: :;-.;::.,...!:'"Jt!i:ytt~~;~liK\~~t;ti3""'J!~J-~.';\~~~t~~f1~~~~~.;~!~~~~;~2~:~~n'J'~n!r~i"" ~~., r,~: i~~f: -J :. .'~. :i . .,~. :: .: ~ ~~ ~ ~~~~, ~. ~ -~ .. . - ...,,- 44 " ' - ~ " " ' - T " ' : : " 7 " " ' ' ' ' - - - ~ , . . . . . ~ :: ~ - .o !r " . .. .< ,; )" -" -~ ,~ . . .:k:!'?::~:"2.l.t~~,' ...

i c o M " 1 . .\ I f 1

1 of OA6.of OA6.l 0 - - t r ' )


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B. Monitor pin 5 of, QA2again. Set the AUTObutton out. Verifythat the AUTOATTACK/RELEASEEDis out. Verify a rectifiedsine wave with waveform peaks that are the same height.(The amplitude will be much greater). Set the AUTObuttonin.C. Apply 100Hz @ OdButo J25-2. Set the STEREOCOUPLERutton~.k; in. 'Verify that the SLAVE(yellow) LEDis lit. Monitor Pin~y{ lS i: F '"""f) . 5 of QA3 in the same manner as Step 3A. Adjust RMSSYM

f~\J-' ~'~~(R59) until the waveform peaks are the same height. YouG ~ -:-::.Jl) should get a near perfect sine wave. Monitor pin 5 of QA2.

, I ~ ~ r r v ' Verify a sine wave similar to the waveform at pin 5 of QA3.L~v D. Monitor pin 5 of QA2again. Set the AUTObutton out. Verifya rectified sine wave with waveform peaks that are the sameheight. (The amplitude will be much higher). Set the STEREOCOUPLERbutton out. Verify that the SLAVE(yellow) LEDisout.5. RMSTRACKINGADJUST

A. Apply +6dBu @ 1kHz to the input of the UUT.Set STEREOCOUPLERbutton in.B. Monitor J25-1. Trim the output of the osc. for OdBuat J25-1. Monitor the cathode side of cR~q1ihdverify approximately60mVDC(BC453 transistor), or 6mVDC(2N3904 transistor).C. Apply OdBu @ 1kHz to J25-2. Monitor the cathode side ofCR8. Adjust RMSTRACKING(R52) for the same voltage at thecathode of CR8 as in Step \ 5B (approximately 60mVDCor6mVDC) \\\_.-\~

6. THRESHOLDEDCHECKr , A. Set the STEREOCOUPLERbutton in.B. Apply 1kHz to J25-_4. Set the osc. for minimum amplitude./6>1 f/j:((}'t(" e y Verify that the BELOW(green LED) is lit. Increase the_ - 1 . - ; ; ; -If amplitude of the osc. until the yellow threshold LED

M O ;> J ..)25 .' /I lights. Verify -18.0dBu at the output of the osc. Increase-f l J . . . . 1 t.Jj{.1! @ P - the osc. amplitude until the ABOVE(red) threshold LEDr . z : , - 1 - : ? / - 1 lights. Verify -9.0dBu at the output of the osc. Furtherm J increase the osc. amplitude until the PEAKSTOPLEDlights.Verify -1.0dBu at the output of the osc.

C. ~~S:~m~D~~'t!~7. VCASYMMETRYDJUST,A. Apply 1Khz @ +12.2dBu (3. 16VRMS)to the,input of the UUT.

t ; , ;11 ; ' 1 } B. Ground the control port of M1 (the VCA)at the local groundm l . . . . . .. of M1. Monitor the output of the UUT.,,1:- C. AdJ'ust R77 for minimum THDat the output of the UUT. THD


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.. .- 8. COMPRESSIONTHRESHOLDCALA. Apply 1Khz @ +12.2dBu (3.16VRMS) to the input of the OUT.B. Set THRESHOLD(R60) to +1O. ~if p ~ r J e - L . .

Set COMPRESSION(R141) to infinite.F(~p~~l HI..ri'lf mechanical adjustment. Power up the OUT., ~{OO~ . B. Apply 1Khz @ OdBu to the input of the OUT.

, Set the METERINPUT button in. Verify that the rear panelMETERCALIBRATION (R125) will vary the front panel metersetting from -10dB to +10. You may have to change the valueof R169 to 680k - 1MEGto meet this spec.

C. Set METER CALIBRATION (R125) for OdB on the front panelmeter.

D. Apply 1Khz @ -20dBu to the input of the OUT. Verify areading of -20dB on the front panel meter.

11. METERCAL (OUTPUTANDGAIN CHANGE)A. Apply 1Khz @ OdBu to the input of the UUT.B. Set METEROUTPUTbutton in.

Set COMPRESSION(R141) to 1.Set THRESHOLD(R60) TO +10.Set OUTPUTGAIN (R135) to O. verify OVdc +/- 200mV atJ25-7. Set R138 for OdBu at the output of the UUT.

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( [ . 1 -- ( "' / '' \'- /D. set METER ZERO GAIN ADJUST (R172) for 0 on the front panelmeter.E. Set METER GAIN CHANGE button in.Set THRESHOLD (R60) TO -40.F. Rotate COMPRESSION (R141) CW until -10 dB is noted on thefront panel meter. Verify -10dBu at the output of the UUT.

12. OUTPUT GAIN RANGE CHECKA. Apply 1Khz @ OdBu to the input of the UUT.Set COMPRESSION (R141) to 1.Set THRESHOLD (R60) TO +10.B. Monitor the output of the UUT. Verify that the OUTPUT GAIN(R135) has a range of -20dBu to 20dBu.13. SYSTEM BYPASS CHECKA. Apply 1Khz @ OdBu to the input of the UUT.Set COMPRESSION (R141) to 1.Ccw

Set THRESHOLD (R60) TO +10. C~Set OUTPUT GAIN (R135) for OdBu at the output of the UUT.B. verify unity gain thru the UUT in with the SYSTEM BYPASSbutton in or out. Set the SYSTEM BYPASS button out.14. PEAKSTOP LEVEL CALA. Apply 1Khz @ OdBu to the input of the UUT.B. Set COMPRESSION (R141) to 1.Set THRESHOLD (R60) TO +10.Set AUTO button in.Set OUTPUT GAIN (R135) for OdBu at the output of the UUT.Set STOP LEVEL (R164) to o. Verify that the PEAKSTOP LED

lights at approximately +5 on the front panel markings.C. Adj ust LIMIT THRESHOLD CAL (R165) full CW. Verify THD< 03% . Adjust LIMIT THRESHOLD CAL (R165) CCW untilTHDreads .1%. (( ' - I-V)D. Apply 10dBu to the input of the UUT. The output of the UUTshould read 5.5dBu (+/-ldB). Monitor the output with ascope and observe that the waveform is "soft clipped".E. Set the STOP LEVEL to +24. The waveform will return tonormal and the PEAKSTOP LED will be off. Rotate STOP LEVEL(R164) CCW until the PEAKSTOP LED lights. The STOP LEVEL(R164) should be at +10 on the front panel markings. Tweakthe STOP LEVEL (R164) further CCW. Clipping should becomeapparent with just a bit more CCW rotation: Return STOPLEVEL (R164) to +24.

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.. 15. CLAMPING CHECKA. Apply 1kHz @ OdBu to the input of the UUT.B. Set COMPRESSION (R141) to 1 Cc"JSet THRESHOLD (R60) TO +10.CL0Set OUTPUT GAIN (R135) for OdBu at the output of the UUT.Set AUTO button in.Set STOP LEVEL (R164) to +24 cv- 'C. Monitor the output of the UUT on a scope. Turn the power ofand then on again. Note that when the power is turned on,the waveform is clamped momentarily, then returns tonormal._,--=,16. FREQUENCY RESPONSE CHECK B. ( y . Y ( \ S )A. Same conditions as step 13A and ~.~ B. Verify flat frequency response (+/- .5dB) in a 20Hz - 20kHz

SV~\ 0 ' - . ) ' bandwidth ..7 r ' u < J .7\/TC. Set COMPRESSION (R141) to infihite. Rotate THRESHOLD (R60)

.s; C Y \ . . ' CCw until 10dB gain reduction is noted.I.!2L- 1)lLi...i.V u__...-';, " /0 D. Verify flat frequency response (+/- .5dB) in a 20Hz - 20kHz~t ~~- bandwidth.

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17. NOISE CHECKA. Same conditions as Step 13A and B.B. Mute the osc. Verify < -93dBu 'noise (-96dBu typical). Usethe 20Hz - 20kHz and the 400Hz filters.18. OUTPUT OFFSET CHECKA. Same conditions as Step 13A and B.B. Verify < 10mVDC at the output of the UUT.19. CLIPPING LEVEL CHECKA. Same conditions as Step 13A and B.l . ( t - / : e . (,ctJ'_Cfi....o j " . B. Load the UUT with 600 ohms .I )

I, T' F C.''j) ..l. O"l'\ ~ f A . . .~ -i-: U ( 1 J f - rt1~/,J 0 / 1 ' IN

i 1 L.&-{J,I f t m f L >t,f -;(.~>

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Increase the level of the osc. until the PEAKS TOP LEDlights. Verify 23bdu at the output of the UUT. Increase thelevel of the osc. further until clipping is attained.Verify 24dBu (+/-2dB) at the output of the UUT. Remove the600 ohm load.

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20. THD CHECKA. Same conditions as S~ep 13A and B.B. Set OUTPUT GAIN (R135) for 20dBu at the output of the UUT.Verify THD < .1% @ 20Hz


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22. ~T H 1 2 . S ~w-=;(_-~f.p,

PRELIMINARY ATTACK AND. RELEASE CHECKA. Front panel knobs settings from step 2lC.B. set ATTACK (R82) to 400dB/MSEC. Q~set RELEASE (R86) to 4kdB/SEC. C(UJSet AUTO button out.C. Mute then unmute the osc. Verify that the front panel meterhas no delay in moving between -20dB and OdB.D. Set RELEASE (R86) to 10dB/SEC.cWMutethe osc. and verify that the front panel meter movesmore slowly (approximately 2 seconds) to OdB.E. Set ATTACK (R82) to ldB/MSEC.c~Verify an increase of ldB at the output of the UUT.

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23. SLAVE CHECKA. This test requires a working l65A and a "slave" cable.B. Connect the two units together with the "slave" cable.Apply 4dBu to the input of the UUT. Set the STEREO. COUPLERbutton in on the working l65A and set the STEREO COUPLERbutton out on the UUT. Verify that all of the front panelfunctions of the UUT are mirrored by the working l65A.Reverse the settings of the STEREO'COUPLER buttons. Verifythat all of the front panel functions on the working l65Aare mirrored by the UUT.C. Set the STEREO COUPLER button out on both units. Verifyindependent operation of both units.

24. ATTACK AND RELEASE TESTA. Mute the osc. at the input of the UUT.B. Set STEREO COUPLER button out.Set AUTO button out.Set GAIN CHANGE button in.Set SYSTEM BYPASS button out.Set THRESHOLD (R60) to +10.Set COMPRESSION (R14l) to infinite.Set ATTACK (R82) to 400 dB/MSEC.Set RELEASE (R86) to 10dB/SEC.Set STOP LEVEL (R164) to +24.Set OUTPUT GAIN (R135) to o.Check J25-7 for OmVDC +/-200mVDC

Note: You will need a storage scope with a 5BlON timebase and a5A18N vertical amp. Nearly any vertical and horizontal ampwill perform this test.C. Scope Set-up.

vertical: DC coupled20mv/DIVCAL full CWHorizontal: .2V/SECSource - EXT.CAL full CWAUTO TRIG - outHook up EXT SYNC of the scope to the syncoutput of the pulse generator.

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D. Connect the pulse generator output to the input of the UUT.Connect the power' BNC of the pulse generator to +15VDC(R14) of the OUT. Connect the control port of the VCA (Ml)directly to the input of the scope. Rotate THRESHOLD (R60)until 120mVDC deflection is noted on the scope (set theTHRESHOLD knob to approximately 0 on the front panel). SetR93 (15 turn pot) for 2 seconds of release time. Verifythat the ramp displayed on the scope is similar to thefigure below. !:tEvp

(! ) - r / lH :f i J a -O - -x 0C 1 J 7 P I l .1 5 ! Ic tJ - 00/ r 1 ff I . f < - - C C W~- ccu l0 ; e t l Y N - 0 ) o v ~ - : r.:ficP U~(_ - Ci


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E. set the ATTACK (R82) to lMSEC/dB. Verify that the rampdisplayed on the scope is similar to the figure below.

6CmV

\./ (---------5 OmSEC"-- "-'_'--'--'--'--.'.......Slowly rotate the ATTACK (R82) CCW. The attack ramp willbecome more vertical as the ATTACK (R82) is rotated CCW.Set the scope to .1ms/DIV horizontal. Verify that the ramp.on the scope is similar to the figure below.

120mV

. - - - - - _ .._----_ . . . . ._ - - - -------

I~{-..-- ----'lmSEc--------------....'(

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A. set the AUTO button in. Set the scope to 20ms/DIVhorizontal. Verify that the ramp on the scope is similar tothe figure below. Disconnect the pulse generator from theUUT.

. . ~ - - - - - - -~~~----------~200mSE~'--------------~25. OPERATIONAL CHECK

A. Apply 1kHz @ 4dBu to the input of the UUT.B. Set COMPRESSION (R141) to 1.

Set THRESHOLD (R60) to +10.Set OUTPUT GAIN (R135) for 4dBu at the output of the UUT.Set AUTO button in.Set STOP LEVEL (R164) to +24.C. Rotate STOP LEVEL (R164) CCW until the PEAKSTOP LED lights.Monitor the output of the UUT with a scope and verify theonset of clipping. Verify that the STOP LEVEL knob lines upwith the +5 mark on the front panel. Return STOP LEVEL(R164) to +24.D. Verify that the front panel meter reads OdB with any meterfunction button in. Set COMPRESSION (R141) to infinite.verify 2dBu at the output of the UUT. Rotate THRESHOLD(R60) CCW until the ABOVE (red) threshold LED is lit. Setthe OUTPUT METER button in. Verify that the front panelmeter reads -7dB(+/-ldB). Verify -2.5dBu (+/-ldB) at theoutput of the UUT. Verify that the THRESHOLD knob lines upwith the 0 mark on the front panel.

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,":j, E. Rotate the THRESHOLD (R60) further CCW until the ,frontpanel meter reads -20dB. Verify -16dBu at the output ofthe UUT. Verify that the THRESHOLD knob lines up w~th the-20 mark on the front panel. Set the GAIN CHANGE button'in.Verify that the front panel meter reads -20. Set theCOMPRESSION knob to 4. Verify that the front panel meterreads -15. Verify -lldBu at the output of the UUT.F. Return the front panel knobs to the settings of 25B.G. Vary OUTPUT GAIN (R135) from +20 to -20 and verify a+/- 20 dB gain change at the output of the UUT. ReturnOUTPUT GAIN (R135) to O. Verify 4dBu at the output of theUUT.H. Set COMPRESSION (R141) to infinite.Set AUTO button out.Verify that the ATTACK (R82) and RELEASE (R86) have an

effect on the distortion trace.

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165 calibration procedure

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