Gates CRITERION Series - Adjustments; 4.1 Recording Amplifier Bias Level

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SECTION 4
4.1 REX;ORDING AMPLIFIER
4.1.1 BIAS LEVEL: When purchal!ling a new record amplifier or replacing
record heads. it w:1ll be necessary to check the bias adjWltaent on the
record amplifier. Since the inductance of the record heads IB&:1' vary tJoa.
head to head, biaB voltage should be readj'wlted ,ach time the record
amplifier is used with. new head or a different playback u:ni t in order to
maintain proper recorded frequency response and output. 'l'be bias &dj118t-
men t should be made uaing tbe type of tape which w1ll normally be ued.
The following procedure should be ued when bia8 adjustments are required:
SET_ UP __ The output of the pll3'back should be connected to a console or any
convenient VU meter. Connect an audio oacilia tor to the record amplifier
input. For :;'oeation of adjustment controls .. e Record Allpl1.t1er Chassis
Layout.
Steps to follow in adjustment--
1. Set the oscillator frequency at 1000 cycles.
2. Insert an erased Jt or .5t minute cartridge in the Playback
Unit.
J. On the Recording Amplifier_Press the Record Set Button and
adjuat the Record Level to -5 VUe
4. While recording, monitor the Playback output and adjust
trimmer CB06 with a non-magnetic 8crewdri vel' for marllIIlIII
playback reading. Readjuat C806 in both a clockwise ard
cO'Ol'lterclockwise direction, untu a t db drop in output i.
noted.. Then adjust to tile exact peak.
NOTE: Re-erase cartridge if un1.t cues.
5. On the Playback Unit Head Assembly __ unplug the green (cue
play) head lead and insert the red (program play) head
lead in 1 ta place. '1'b.1s pem1 ts IIOni to ring or the cue track
from the playback output while ca bia. adjuta.nt. are be1nc
made.
6. Remove the cover from 160j in the Record Amplifier and
1I1&I"1ual.l.y operate the relay. 'l'b1s will eauae 1000 eycle. to
be recorded on the cue track.
7. While manuaJ.ly operating 160). &d~t tn.aer <:50.5 with • nDn...
aagnetic Bcr81Kir1ver for IUX1.mta playback re&dinK. UteI' th.
peak adjustunt hall been reached, turn ca05 ccnmtereJ.odnr1 ••
until th. output reading hu dropped It db. LA" CBOS
ad justed to th1.I aet tin«.
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