eXact 240 - 2.3 Circuit Description

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240 -066 4
SECTION I I -- - --- - - --- - - - - - --------- - - -- -- --- - -- - - -- --- ---- -- MAINTENANCE
2.3 CIRCUIT DESCRIPTION
2 . 3 . 1 POWER SUPP LY
THE THREE POWER SUPP LIE S ARE ALL BASED ON THE SAME PRINCIPLE:
A DC AMPLIFIER IS REFERENCED TO A S TANDARD VOLTAGE (A 5651
GAS TUBE OR PRECISION DIVIDE RS FROM - 210V) . ANY VARIATION
FROM LI NE OR LOAD rs AMPLIFIED BY THE DC AMPLIFIER AND PASSED
AL ONG AS A C ON TRO L VOLTAGE TO THE SERIES REGULATOR T UBE . THE
FILA MENT SU PPLY I S REGU L A TED BY A TR~NS!S TOR REFERENCE D TO A
Z
ENER DIODE.
2.3 . 2 S Q UARE W~ VEFORM GENERATOR
(A) V105 IS A CATHODE COUPLED MU L TIVI B RATO R. ITS OUTPUT
(PIN # 6) SWINGS FROM BELO W -1 00V , WHEN V105B IS CONDUCT-
IN G , TO +100V WHEN IT I S CUT OFF. THE TIME DU RATION OF
EACH HAL F -CYCL E IS DETERM IN ED B Y THE TRIANGLE WAVEFORM AT
GRID P IN #9 OF V10 5 A · THE TRIANG LE NOW DETERMINES THE
SWITCH ING OF THE M UL T I VIB RAT OR . THE TRI A NGLE M UST ALWAYS
PASS THROUGH THE SAME DC LEVELS TO SWITCH V105 AND THERE-
FORE THIS PARTLY DETERMINES THE TIMING OF THE INSTRUMENT .
(B) THE LOOP GAIN OF THE CATHODE COUP LED MULT[V!BRATOR rs DE-
TE RM INED BY I TS CATHODE CURRENT . THIS DETERMINES THE
FINAL TIMING AND IS CONTROLLED BY R1 05.
(c) V1018 I S A CATHODE FOLLOWER WHOSE OUTPUT HAS THREE FUNC-
TIONS:
(1) SQUA RE WA VE S YMMETRY ( X10), R111 PROVIDES FOR EQUAL
VOL T AG E BUT OPPOSI T E POLARITY AT X10 E ND OF CYCLE S /SEC
DIAL F OR EACH HALF-CYCLE OF V105 .
(2) PROVIDES ST AN DARD SQU AR E WA VE TO OUTPUT CATH ODE FOLLOW-
ER V101 A.
(3) PROV IDE S SQUARE WAVE TO MI LLER INTEGRATOR T IMING RE-
SISTORS AND CAPACITO RS (R134-R136 AND C1 02A - F).
2.3 . 3 TRIANG LE WA VEFORM GENERATOR
V102 IS A M ILLE R INTREGRATOR AMPLIFIER WITH AN ASSOCIATED
CATHODE FOLLO WER . THE SYMMETRICAL S QUARE WA VE FROM V101B IS
FED TO GRID PIN # 2 OF V102 AND THE INTEGRATOR ACTION PRODUCES
A TRIANGLE WAVEFOR M AT THE CATHODE (PIN #8 OF V102). TIME
CONST ANT S FOR THE INTEGR ATO R ARE C102 (A -F), R116 AND R134,
R135 , R136. MILLER DC BAL R13 2 DETERMINES THE LEVEL AND AMP -
LIT UDE OF THE S IGNAL BEING F ED BACK TO THE GRID PIN #9 OF V105 .
2.3 . 4 SINE WA VE FORM GENERAT OR
V104 IS A PENTODE WHOS E BIAS CHARACTER ISTICS ARE ADJUSTED BY
THREE S I NE SHA PI NG A DJUST MENTS , R139, R143 AND R145 . THE
LINE AR TRI AN GLE FROM V102 IS SHAPED BY THESE ADJUSTME NT S TO
PRODUCE A VERY LOW DISTORTION SINE WAVE AT THE PL AT E PIN # 5 ·