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SETTINGthe PICO’ssignalgain.
H) Withthe0dBUreference tonesappliedtothePICO’sXLRinputs, adjustinput
sensitivitypresets R37 and R38 togiveexactly“4”againoneachmeter. Theseare THE
ONLY controlsthatshouldadjustedtonormalisethePICO’ssignalgain.
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I) ConfirmthatthePHASE LEDislit GREEN. AlterthePHASE switchontheAudio
Generator, andconfirmthattheLEDchangestoRED, andthatthedisplayedaudioleveldoes
notaltersignificantlyoneithermeter. ResetPHASE tothenormalcondition.
J) AdjusttheaudioOPlevelfromthegeneratortogiveareadingof+8.15dBprecisely
ontheaudiolevelmeter. AdjusttheREDLEDtriggerthresholdpointcontrol“P2”toensure
thattheLEDsare just illuminated. Reduce theGENERATOR outputto+8.1dB, andensure
thatboththeLEDsextinguish.
Note: VERY small balancingadjustmentstotheinputsensitivitycontrols(R37 &R38)
maybemadetoachievethiscondition, butnotsomuchastoaffectthedisplayeddeflectionof
“4”, whichisabsolutelyfundamentaltocorrectoperationofthePICO.
Checkthatthemetersareindicatingavalueofapproximately“6”onthescale. Thereis
noadjustmentforthisrequirement, whichisentirelyafactorofthemeter’slinearity. Anyerror
thatexceedsacoupleofpointerwidths(at“6”)mayindicatethatthemetermovementisout
oftolerance, andwill requirechanging.
K) Reduce theoscillatoroutputtoapproximately-25dB, andconfirmthatthePHASE
LEDisextinguishedwithinasecondorso, whenthemeterhasreachedasteadystate. The
lampshouldcertainlybeextinguishedby-30dB.
Whensatisfied, returntheoscillatoroutputtothestandardlevel, 0dBUprecisely.
L) CheckthephaseintegrityofthePico’saudiooutputloopwiringforA1&A2, by
usingapairofXLR3maletofemalecablestofeedtheloopedsignaltoa second Pico. Ensure
thatthePHASE LEDonthesecondPicoisilluminatedGREEN, andthattheaudiolevel
indicatedonALL metersis“4”.
Itisparticularlyimportantthattheaudiolevelsdonotaltersignificantly. Anyvariation
thatoccurswhenthesignalisloopedtoasecondPicowouldsuggestanoutputwiringerror.
Notethatisdoesnotmatter(atthisstage)thattheoutputwiringofthesecondPico
hasyettobeconfirmedascorrect, since preliminarytestingup tostage“I”, will have
confirmedcorrect input wiring.
M) Whentheoutputwiringhasbeenconfirmedas correct forthetestedUnit, swapthe
PicoUnits, andconfirmthattheoutputwiringiscorrectfortheUnitoriginally usedtocheck
outputPHASE. Afterthisprocess BOTHUnitswill beconfirmedascorrect. Eitherofthese
testedPicosmaythenbeusedforsubsequentoutputwiringtesting, withoutfurtherrepeating
this“M”stepinthisparticularbatchtest.
IssueV2.1
TonyDrummond-Murray
21/09/2009
Murraypro PicoPPM AlignmentV2.1
Page2