CRL PMC-450, Installation And Operation Manual

Page 1: ...LATION CONTROLLER I FOR AM BROADCAST I INSTALLATION AND OPERATION MANUAL I I I I I I I I I I I I el THE PROFESSIONAL S CHOl CE SYSTEMS Circuit Research Labs Inc 2522 West Geneva Drive Tempe Arizona 85282 3192 U S A 1800 535 7648 j602 438 0888 FAX 438 8227 ...

Page 2: ...ematic drawings reproduced in this manual contain p r o p r i e t a r y d a t a t o C i r c u i t Re se a r c h Lab s I n c T he u se r o f t h i s manual agrees to make no disclosure reproductions or use of any pa r t o f t hes e d raw i n gs except by pr i or w r i t ten perm i s s i on f r om Circuit Research Labs Inc P N PMC 450 10082 CIRCUIT RESEARCH LABS INC 2522 W Ceneva Drive Tempe AZ 8528...

Page 3: ...Line Connections Unbalanced Line Connections 2 18 INITIAL SET UP General Set Up Procedure Asymmetry Set Up Tilt Correct Set Up Auxi I iary Output Day Night Operation 2 31 GUIDELINES FOR SYSTEM SOUND SETTING 3 OPE RAT ING INSTRUCT IONS 3 1 GENERAL 3 3 FRONT PANEL CONTROLS SWITCHES INDICATORS Powe r L ED I nd i ca to r G R Input AGC Switch Mid Range Presence Hi Freq Equalization Input Level Indicato...

Page 4: ...REMENT 6 7 6 24 TOTAL HARN tONIC DISTORTION 6 8 6 25 FREQUENCY RESPONSE 6 8 6 26 SIGNAL TO NOISE NOISE RATIO 6 8 6 27 INTERN tODULATION DISTORTION 6 8 6 28 TROUBLESHOOTING 9 General 6 9 Suggested Component Checks 6 9 6 34 CUSTa 11ZATION 6 11 6 43 FACTORY SERVICE 6 14 7 APPENDIX A B c D E F c SYSTEM INFORN ATION PARTS LISTS BLOCK DIAGRAM PC BOARD LAYOUT DIAGRAM SCHEN ATIC DIAGRAMS FRONT PANEL CONTR...

Page 5: ...RATIONS BALANCED LINE CONNECTIONS UNBALANCED LINE CONNECTIONS NORMAL M DULATION ENVELOPE UNDER CORRECTED M DULATION ENVELOPE OYER CORRECTED M DULATION ENVELOPE TYPICAL TRANSMITTED SPECTRUM COv PARISON NRSC PRE EMPHASIS NRSC STOPBAND SPECIFICATION BASS PRE EMPHASIS FILTER RESPONSE OUTPUT SPECTRUM OF PMC 2 2 1 2 2 2 5 2 7 2 7 2 1 3 2 1 3 2 1 4 3 5 4 3 4 3 5 4 5 7 PMC 45O C Co py r i g ht Ci r c u i ...

Page 6: ...t y for the cu s tomer s f ailure to comply with these requiremen t s 1 5 RE AD i ns tructio ns ALL INSTRUCTIONS Al I safety and operating should be read be f ore the equipment is operated 1 6 GROUND AND POJVER CONNECTIONS To minimize shock hazard this equipment must be connected to an electrica l ground Grounding is accomplished by proper use of the three conductor AC power cable supplied with th...

Page 7: ...tion Selectable Low frequency Tilt Correction Circuit Improves the Modulation Capabi I ity of Many Plate modulated Transmitters 22 dB Range 10 Segment Input Peak Indicator Programmable 1 dB step Peak Limiting Control Rugged 1 3 4 Rack mount Chassis With Integral RFI Protection Adjustable High Frequency EQ Adjustable Mid Range Presence 1 16 The CRL PMC 4 50 i nco r po r a t e s de s i gns o r i g i...

Page 8: ...vel by several percent 1 21 Progranmable 1 dB per step peak limiting circuitry i s provided with a range from Oto s dB This circuitr y s e I e ct s t he amount o f i n s tan tan e o us ga i n reduct i on I i mi t i n g applied to the audio signal 1 22 To aid the user in properly setting the audio into the unit a 10 segment peak reading LED input meter with a range from 20 to 2 dB is provided overl...

Page 9: ...PoweredRadio Com FIGURE 1 1 TYPICAL TRANSMITTED SPECTRUM Laboratory transmitter 15 minute peak store display V 10 dB div H 10 kHz div 300 Hz resolution PMC 450 C Copyright Circuit Research Labs Inc 1989 Page 1 4 ...

Page 10: ... OF NEGLIGENCE BREACH OF WARRANTY OR OTHERWISE THIS DISCLAIMER OF INCIDENTAL OR CONSEQUENTIAL DAMAGES It K LUDE S BUT IS NOT LIM ITED TO PROP ERTY DAMAGE S LOS S OF PROFITS LOSS OF TIME OR OTHER LOSSES OR INCONVENIENCE RESULTING FR 1 ANY DEFECT IN THE MATERIAL OR V ORKMANSHIP OF THIS PRODUCT OR ANY OTHER CONNECTION WITH THE PURCHASE OPERATION OR USE OF THIS PRODUCT S 1E STATES DO NOT ALLO V THE EX...

Page 11: ...iver manufacturers and the trade press can be informed as to the progress of conversion to the voluntary national standard 1 34 If this card is missing notify Circuit Research Labs Inc or National Radio Systems Corrmittee c o NAB Science Technology 1771 N Street N W Washington D C 20077 6316 PMC 4 5O C Co p y r i g h t C i r c u i t Re se a r c h L a b s I n c 19 89 Page 1 6 ...

Page 12: ...put output 5o Hz t o 8 kHz o 1 5 d B 3 dB at 9 5 kHz 30 dB atten at 10 5 kHz 4 0 d B a t t e n a t 1 1 0 kHz Conforms to NRSC standard using required dynamic measurement method 50 Hz to 10 kHz 0 1 5 dB 3 dB at 11 kHz 30 dB atten at 13 5 kHz 50 Hz to 15 kHz 0 5 dB 10 dBm input output 20 kHz bandwidth 0 25 over selected operating bandwidth at or below 100 negative modulation level o 1 65 dB in opera...

Page 13: ... level meter with a 22 dB 28 dB with OVLD dynamic range 2 I I imi t i nd i ca to r s mo n i t o r a c t i v i t y of patented overshoot corrected filter circuitry 32 to 122 degrees F 0 to 50 degrees C 100 130 or 200 250 VAC 48 440 Hz 20 VA maximum EMI suppressed IEC connector standard 0 95 RH non condensing 0 1 5 00o feet AMS L 18 lbs including standard accessories 19 48 3 cm W 1 75 4 5 cm H 16 4 ...

Page 14: ...OWER UP OF THIS UNIT Peak Modulation Controller s FIGURE 2 1 PMC 450 FRONT PANEL A 11 0U1 UI O a H U t J uoO H I I U I l I 0 2 1 1 ol3leleleleJeJeJeJeJeleJeJelelo 1111 1 o e C J 0 FIGURE 2 2 PMC 450 BACK PANEL 2 3 BEFORE POWER UP 0 1 Se t th e power I ine module as p e r Section 2 4 C 0 CRL SISHMS H r 11 JH 2 Set the internal jumpers as required for the intended s y s t em a pp I i c a t i on a s ...

Page 15: ...ining the fuse and the PCB voltage selector by pushing in on the raised the power plug receptacle lever adjacent to Remove t he PCB v o I tag e s e I e c to r and po s i t i on i t the red I ine on the edge of the PCB corresponds opening in the cover opposite the legend f or the line voltage so that to the desired 3 I n s e r t t h e PCB v o I t a ge s e I e c t o r f i r m I y i n t o t h e mod u...

Page 16: ... p r e s en t s an impedance of l0K ohms Jl0 OUT BASS CLIP JUMPER This jumper selects the low frequency response of the input leveling AGC c i r cu i try I n the OUT po s i t ion the I ow frequency response is flat In the IN posi tion the G R circuits do not respond to frequencies below 100 Hz The OUT position i s rec onme n ded for mos t a pp I i cat i on s Jll IN BASS PRE EMPHASIS JUMPER The IN ...

Page 17: ...VDC Fixed measure at TP4 50 mVDC DS2 1 5 VDC Fi x ed measure at TPS 50 mVDC GATE LED INDICATOR This LED is illuminated when the gate circuitry is activated This f reezes all gain control action when the level drops below the gate threshold 20 dB LED DESCR I PT ION DS 3 Gate Indicator 2 11 INTERCONNECTIONS 2 12 GENERAL 2 13 Th e PMC 4 50 i s d e s i gn ed t o i n t e r f a c e w i t h ma n y t y p ...

Page 18: ...L f AGC400 STUDJO AUDIO AGC CAL STL SEC400 4 BAND R ECEIVER COMPRESSOR OPTIONAL Al USE WITH MONAURAL STL EQUALIZE TELCO LINE CAL CAL SEC400 __ PMC450 4 BAND AM COMPRESSOR LIMITER lll TIONAL Bl USE WITH TELEPHONE LINE CAL AGC400 AGC CAL SEC400 4 BAND COMPRESSOR OPTIONAL CAL PMC450 AM LIMITER Cl CO LOCATED STUDIO TRANSMITTER SITE __ CAL PMC450 AM LIMITER MAIN TRANS MAIN TRANS MAIN TRANS ...

Page 19: ...f or operation with unbalanced line equipment The PMC 450 has one i n put and one ma i n output connect i on An aux i I i a r y output connection is also provided for driving a second transmitter NOT E Wh e n u s i n g t he u n b a I a n c e d I NPUT c o n n e c t i o n o n I y t he shield is connected to the ground terminal and the negative terminal is connected to the ground by a jumper w i re a...

Page 20: ...R AUX TRANSMITTER FIGURE 2 5 BALANCED LINE CONNECTIONS INPUT OUTPUT GND GND 41 J _ INPUT OUTPUT AUX OUT GND I _ _ _ OUTPUT TO NIGHT OR AUX TRANSMITTER DO NOT CONNECT FIGURE 2 6 UNBALANCED LINE CONNECTIONS PMC 4 50 C Co p y r i g h t C i r c u i t Re s e a r c h L a b s I n c 19 8 9 Pa ge 2 7 ...

Page 21: ... on 2 11 3 Ve r i f y t ha t t he i n t e r n a I j ump e r s a r e s e t p r o p e r I y a s p e r Section 2 6 2 21 SET UP PROCEDURE 2 22 IN I TIAL CONTROL SE T TINGS CONTROL OR SWITCH INPUT AGC G R MID RANGE PRES E NCE SET T ING HIGH FR EQUENCY EQUALIZATION TILT CORRECT LIMIT I NG OUTPUT LEVEL ASYIY METRY INPUT CALIBRATE BANONI DTH PROOF OPERATE 9 S Out OP ERATE Located on back panel 8 FULL Y cc...

Page 22: ...he input sensitivity may ne e d to be adj u sted see Section 6 4 3 I n c r ea se t he s e t t i n g o f t he OUTPUT LBVBL con t r o I f r on t p an e I c I o ckw i se u n t i I t he neg at i v e mod u I a t i on peak s a s obs e r v e d on the mod u I at i on mo n i tor or o s c i I I o scope are peaking at 90 9 5 The setting of this control is d i ct ated by the neg at i v e mod u I at i on cap a...

Page 23: ...k modulation to be set accurately 3 4 I f t he as ymme t r y cont r o I i n c re as es neg at i v e mod u I at i on check for phase reversal of PMC outp u t connections Re t u r n t he GIR and LIMITI NG sw i t ch es to t he no r ma I I y used positions 2 25 TILT CORRECT SET UP NOTE NOTE This procedure should be done only after all other adjustments have been completed This adjustment can be p er f...

Page 24: ...oscope or mod u I at Ion mo n i tor Th e d i sp I a y w i I I be hi g h I y clipped as shown in the fig ure s on the fol lowing pa ge TO AVOID DAMAGE THE TRANSMITTER SHOULD BE OPERATED FOR A FEW SECONDS AT A TIME ONLY WARNING NOTE I f t he mod u I a t i o n en v e I ope as viewed on the 7 8 osci I loscope appears as in correction is necess a ry and Figure 2 7 t he f o I I ow i n g no ti It procedu...

Page 25: ...70 as obser ved on t he mod u I a t i on mo n i to r o r o s c i I I o s cope 4 Increase the PMC INPUT LBVBL contro l such that the OVLD indicato r flashes to a point where it is illumi nate d most of the t i me w i th p r o g ram au d i o p resen t I n c re as e the settings of the PMC G R and LIMITING switches to maximum s et t i n g s 8 and 5 r esp e c t i v e I y D emodu I a t ed au d i o wi l...

Page 26: ...dio Com I I I I I I I I I I I I I I I I I I FIGURE 2 7 NORMAL MODULATION ENVELOPE No Tilt Present FIGURE 2 8 UNDER CORRECTED MODULATION ENVELOPE Tilt Present I PMC 450 C Copyright Circuit Research Labs Inc 1989 Page 2 13 ...

Page 27: ...e to ve ri fy that the majo ri ty of f re q u ency t i I t i s removed u BE CAREFUL NOT TO OVER CORRECT AS SHOWN IN WARNING FIGURE 2 9 DAMAGE TO THE TRANSMITTER MAY u RESULT IF TILT IS LEFT SICNIFICANTLY 8 9 OVER CORRECTED If th i s adjustment cannot be successfully waveform i n i t i a I I y t i I t s i n the manner as 2 1 1 the t ran sm i s s i on s ys t em r eq u i res see METHOD 1 Step 110 mad...

Page 28: ...tput level of the PMC 400A should never be set such that the negative modulation capablllty of the transmitter Is exceeded NOTE The asymTietry has been previously set for the ma in transmitter in Section 2 24 Verify that the auxiliary transmitter is capable of the positive peak modulation previously set for the main transmitter I f the positive peak capability is significantly less t ha n t he ma ...

Page 29: ...unction with any of the above control settings the dynafex noise reduction circuitry can be activated The f r o n t p an e I TBIUJSBOLD con t r o I s hou I d be s e t t o ob t a i n t he ma x imum amount o f noise reduction during program pauses w i t hou t aud i b I e exp ans i on a r t i f a c t s I t may be des i r ab I e to ch an ge the po s i t i on s of i n tern a I jumper s J11 and J 19 to ...

Page 30: ... 6 M BOTH 6 M C 2 1 0 f t 3 6 s WIDE 6 s L 2 1 I Beauti ful Music Hea vy 9 M DUAL 9 M C 6 2 I Medi um 6 s BOTH 6 s C 4 1 SO f t 3 s WIDE 3 s C 2 0 Country I Heavy 9 F DUAL 9 M C 6 3 Medi um 6 M BOTH 6 M C 4 2 0 f t 3 s WIDE 3 s C 2 1 I Talk Heavy 1 2 M DUAL 1 2 M L 6 4 Medi um 9 M BOTH 9 M L 4 3 I so r t 6 s BOTH 6 s L 4 2 Classical I Hea vy 9 s BOTH 9 s C 4 2 Medi um 6 s BOTH 6 s C 2 1 SO f t 3 s...

Page 31: ...much as 4 dB below the calibrated input level If the input level drops 6 dB the output wi 11 drop only 2 dB Input s i gna I s may i n c re as e as much as 1 5 dB above the 0 dB i n d i ca t i on on t he LED i nput I eve I mete r and not be a f f ect e d by the set t i n g of t h i s sw i t ch s i n c e C R ac t i on i s au t oma t i c above o Proper setting o f this switch is determined by t he so...

Page 32: ...on due to transmitter or antenna de f iciencies the B1 PABQ BQUALIZATION control should be rotated counter clockwise towards the OPP po sition an d u s e d t o t r oub I e shoo t t he s y s t em I f t h i s i s necessary the user s hould determine the rea son f o r no t be i n g ab I e t o u s e t he NltSC s e t t i n g so t ha t t he p r ob I em ca n be co r r e c t e d Ce n e r a I I y t he i na...

Page 33: ...ou s gain reduction limiting applied to the audi o s ignal Lower settings 0 1 or 2 will p rovide well cont r o I I e d but I es s dense pro g ram au d i o Hi gher sett i n gs 3 4 or 5 wi I I p rod u c e ver y dense and I o u de r bu t st i I I tight l y controlled audio The setting o f this sw itch is e n t i r e I y up t o t h e u s e r dep end i n g o n t he d e s i r ed o n a i r apparent loudn...

Page 34: ... i s a d up I i ca t e o f t he O d8 i nd i ca to r s e gmen t on t he f r on t pane I le vel meter 3 30 BANONIDTH SELECT SWITCH 3 31 This switch selects the cutoff frequency of the internal low pass filter In the STD out position a 9 5 kHz f ilter characteristic is enabled corresponding to the NRSC s t o p b a nd sp e c i f i c a t i o n I n t he kHz p o s i t i o n i n t he PMC do e s no t c on ...

Page 35: ... I I y o n t he PCB see Sec t i on 2 6 Th i s f unc t i on i s not no r ma I I y r eq u i r ed with transmitters that do not have a plate modulation transformer The PMC will work without using the tilt correction circuitry however higher peak modulation capability will likely result when the circuitry is enabled and correctly adjusted as required see Section 2 25 3 36 AUXILIARY OUTPUT LEVEL CONTRO...

Page 36: ...i s t i c s o f AM b r o ad c a s t s A ma t c h i n g o f p r e emp ha s i s and de emp has i s i s exp e c t ed to imp rove t he consume r s overall satisf action with the technical qualit y of li s tening t o AM radio 4 5 Most AM stations have used p r e emphasis to varying extents This pre emphasis is employed in an attempt to compensate for the n a r row response of most Al A rec e i v er s I...

Page 37: ...incentive for the further building of AM wideband receivers 4 10 The specification of the chosen stopband characteristic is shown graphically in Figure 4 2 It is implemented through the use o f app r op r i a t e and ca r e f u I I y des i gn ed au d i o I ow pas s f i I t e r s as the final filtering prior to modulation Compliance is measured dynamically to take all audio processing functions int...

Page 38: ...USE AC ALSO 5 5 Power trans f ormer Tl is a triple output with a center tapped winding for the 15 volt supply This winding on Tl provides the operating voltages for the ful I wave bridg e recti f ier consisting of CR3 CR4 CRS and CR6 The p u I s a t i n g DC v o I t a ge i s f i I t e r e d b y C 10 an d C 11 The DC v o I t a ge f r om t he r e c t i f i e r i s f ed to v o I t a ge r e gu I a to ...

Page 39: ...r ee o u t p u t s a r e p r o v i d ed f r om U5 Th e signal may be monitored at US pin 1 pin 7 A The output of US pin 1 is applied to the le f t ch an n e I meter amp I i f i er U4 p i n 2 V4 i s a rec t i f i er that prov i des a DC s i gna I for D i sp I a y Dr i v er U 1 I o ca t e d on PCB 80575 Thi s pulsating DC signal may be monitored at the cathod e of CR13 B T he se c o nd ou t p u t f ...

Page 40: ... the release time of the AGC circuit The other half of Ull is not u sed It it terminated to prevent it from causing noise 5 16 See schematic page 1 and FRONT PANEL CONTROL BOARD schematic The display board is used to acquire the GATING s i gn a I Wh en e v e r p i n 1 o f U 1 goe s t o a h i gh s t a t e t he 2 0 signal i s output to Q6 though J1 14 and resistor R19 When Ul pin 1 i s in a low stat...

Page 41: ... I y c I ockwi se up to 2 dB more pre emphasis at lOkHz is added as measured at pin 1 of U1 2 t ha n t he NRSC p r e emp has i s de ten t po s i t i on 5 20 TRI BAND LIMITER 5 21 The crossover fr equencie s for the tri band l i miter are lkHz and 4kHz 5 22 Refer to schematic page 3 The output of U20 pin 1 is applied to a diode peak limiting circuit composed of CR23 CR22 C90 C91 and R163 Its functi...

Page 42: ...t er sect I on con s i s t s o f component s U 18 Q2 2 Q 2 3 Q24 R157 C8 5 and C86 U18 f unctions as a VCR Voltage Controlled Resistor Wh e n t he p ea k v o I t a g e a p p I i e d t o Q2 2 o r Q24 i s g r ea t e r t ha n 6 vo l ts the transistors will begin to conduct 5 27 Both the po sitive and negative peaks are limited The resulting current charges C85 through resi s tor R157 Control c u r r ...

Page 43: ... Th e output o f L7 is terminated by R135 and is also connected to a shelving f ilte r composed of R278 R277 and C188 This filter i s the f inal component used to implement the NRSC pre empha s i s It also minimize s high f requency overshoots in the transmitter 5 33 Overshoot correction fo r thi s f ilter is prov ided b y t r a ns istors Qll Q12 Q18 and Q19 5 34 The clipping threshold for Q19 is ...

Page 44: ...n e c es s i tat e mo n i tor i n g t he amp I i t u de and p has e o f a s yrrme t r i ca I peak s The r e f o r e po I a r I t y switching t echniques that generate noise are not required 5 39 If there is question as to the presence of asyrrmetry on the modulated RF carrier refe r to th e Troubleshoot ing section of the manual for fur th e r assistance 5 4 0 The o ut put of the f ilte r i s appl...

Page 45: ...i n 5 h a s s i g n a I i mp r e s s ed on i t f r om t he PROOP OPBRATB switc h U t 3 p in 7 i s u sed as the buffer for the other hal f of U 13 whi ch serves as the t ilt correction amplifier The output o f U13 pi n 1 is applied to the MONO OUTPUT control R3 31 T he output of the control drives the d i f f e re n t i a I o u t p u t amp I i f i e r U 14 10 0 ohm r es i s to r s R 10 6 and R108 a...

Page 46: ...ators are secure and in good working condition 3 Remove any d i r t or dust around the uni t This may not irmiediately affect the Unit I but long term exposure may 4 Ke e p a I I I i q u i ds away r rom t he un i t Ac c i den t a I s p i I Iage ca n re s u I t i n s e r i ou s dama ge t o t he un i t and w i I I vo i d the warranty 6 3 ALIGNMENT PROCEDURES 6 4 EQUIPMENT REQUIRED AG Sl AUDIO GENERA...

Page 47: ...ear OPERATE down M NO TILT CORRECT rear FULL CON M NO OUTPUT rear FULL CCW 6 10 INTERNAL CONTROL SETTINGS NOTE Do not change the factory setting unless there is factual informatlon indlcating circuit maIfunction Please contact CRL for further assistance R62 R146 R30 5 mi d ra nge 6 11 POWER SUPPLY CHECK 220 VAC CHECK Set Power Mod u Ie vo I tag e se Ie ct or to 220 VAC po s i t i on Me a s u r e v...

Page 48: ...Check PMC 4 50 f ront display OVERLOAD LED o ff AG 51 to 10 dB ATTE N Move J9 to BRIDGE DM 11 reading 9 25 to 9 75 dB Move J9 to TERM Connect Di YM probe to TP 7 DM 11 reading 6 5 to 7 0 dB 6 13 CATE CIRCUIT TEST AG 51 to 31 dB ATTE N Check PMC 4 50 GATE LED on Ie r t r ea r sec t i on o f PCB AC 51 to 30 dB ATTE N Check PMC 45 0 GATE LED o ff 6 14 C R TEST PMC 450 G R switch s et to o Di YM set t...

Page 49: ... rear side o f R67 Dtvt A reading 12 25 to 12 75 dB Mo ve J 11 t o IN DM I reading 9 25 to 9 75 dB Mo ve J11 to OUT 6 16 LIMITING TEST AG 51 to 400 Hz PMC 450 Dtvt A reading l IM IT INC rear side R67 1 o 75 to 11 25 2 9 25 to 9 75 3 7 75 to 8 25 4 6 4 5 to 6 9 5 s 4 50 to 5 25 PMC 450 LIMITI NG switch to o dB dB dB dB dB 6 17 NRSC PRE EMPHASIS CALIBRATION AND TEST Check D YM probe on rear side of ...

Page 50: ...1 dB approx Dtvfv probe to I e ft side of R158 D reading 17 0 to 1 8 0 dB AG Sl to 4 5 KHz D N 1 reading 13 0 to 14 0 dB DMYI probe to r i g ht s id e 0 f R129 DMYI reading 5 1 dB approx D N 1 probe to TP 9 D A v reading 2 5 to 3 5 dB 6 18 MID RANGE PRESENCE CALIBRATION Check D N 1 probe to TP 9 Check DMYI set to AC DECIBELS AG Sl to 200 Hz Dtvfv R ELAT I V E sw i t c h I N PMC 450 MID RANGE PRESE...

Page 51: ... e o f R 1 39 DM v I r ea d i n g 1 3 7 t o 1 4 5 VDC r ememb e r r ea d i n g DMv probe to le ft side o r R140 Adjust R146 ror same NEGATIVE voltage as front side o r R 13 9 within 01 vo lt s PMC 4 50 L IMIT I NG sw i t c h t o 5 AC Sl to 1 KHz Check PMC 450 f or both LIMITING LEDs on AC 51 to 100 Hz 0 dB ATTEN PMC 45 0 G R SW i t Ch to 8 Oscilloscope probe to I e r t s Ide 0 f R196 Adjust PMC 45...

Page 52: ...neg at i v e peaks PMC 450 iYONO TILT CORRECT rear f ul I CON Move J 17 to OUT PMC 450 YONO OUTPUT control rear tu 11 CON 6 23 PREPARATION FOR SPECIFICATION MEASUREMENT PMC450 co ntr ol settings G R switch o LIMITING switch o MID RANGE PRESENCE control O HI FREQ EQUALIZATION control OFF TILT CORRECT control OFF ASYt AY ETRY control fu l I CON PROOF OPERATE switch rear OPERATE down BANDNIDTH rear t...

Page 53: ...FREQUENCY RESPONSE 400 Hz REFERENCE LEVEL PMC 450 G R switch to o AG 51 to 20 dB ATTEN 6 26 SIGNAL TO NOISE NOISE RATIO 400 Hz REFERENCE LEVEL PMC 4 50 C R sw i t c h t o 0 OPERATE tv ODE MIN 6 5 dB PR00F N ODE M I N 7 5 d B 6 27 INTERMODULATION DISTORTION PMC 450 AC 51 to IM SIC 1 0 dB ATTEN AA 51 to liYD 3 RANGE C Copyright Circuit Research Lab s I nc 1989 Page 6 8 ...

Page 54: ...fraid to li sten to the unit whi le it is in operation A pair of good quality 600 ohm or higher impedance headphones can be used to bridge across the input and output Listening ca n quickly locate a bad unit or clear a suspected unit 6 31 SUGGESTED CO v PONENT CHECKS 6 32 This section lists typical f ailure condit ions f o I I owed by component s and other fa ctor s that could caus e t hat f a I I...

Page 55: ... is play No asynmetry control No positive peak s above 100 Asyrnnetry control not f ully counter clockwise Replace U14 or U13 De fe ctive PROOF OPERATE switch Check 1 0 connections Replace U11 U9 module EQ pot bad Check HI FREQ EQUALIZATION control Replace U12 Bad HI FREQ EQUALIZATION control Replace U6 Replace Ul U2 on displa y PCB Bad asyrnnetry pot Ve r i f y s ymp t om w i t h osci I loscope a...

Page 56: ...sistor was chosen WARNING Do not use solder wick or any other type of utility that sinks large amounts of heat away from the Iron Doing so may damage the solder pad and circuit foll THE WARRANTY WILL BE VOID Use a solder sucker such as a PALADIN 6 40 PROCE DUR E 1 Remove t he e i g ht Ph i I I i p s screws f r om the top o f the PMC 4 50 Remo v e t he I i d a nd se t i t a s l de 2 On the ma i n P...

Page 57: ...POLE at the specified resistor l ocation to either for this 11 Solder the two attached resistors to the other solder pad a s s o c I a t e d wi t h t h i s mod i f i ca t i o n 12 Power up the PMC 450 13 Send program audio containing voice material into the PMC 45 0 and I isten to the outputs with headphones or a monitor system while switching the two chosen re sistors back and forth Use var 1ous ...

Page 58: ...e voices wi I I remain l o u d but will still co ntain a bit o f audib l e IM distortion With val u es o f lOOK to lSOK the IM distort i on wi I I be reduced more Values above 1 50 K w i I I a f f ect the I o u d n es s o I the v o i c es more d rasti ca l ly PMC 4 50 C Copyright Circuit Research Labs I nc 1989 Page 6 13 ...

Page 59: ...d with the ret u rned unit 1 T he ret ur n authorization numb er CLEARLY MARKED ON THE OUTSIDE o f the shipping container See example below 2 Desc r iption of trouble which includes a The symptom description b The un i t swit ch settings when the trouble was detected c A short descripti o n of the facility in which the u nit is used 3 App r ox i mate date o f p u r ch a s e and the s er i a I n um...

Page 60: ...the con sol e and the phone l ine s or aura l STL with the other units at the transmitter s ite The O dB input i ndicator segment shou l d flash on peaks and the red OVLD LED should not flash wit h norma l prog r am ma ter I a I SEC 400 G R L IM I T COv PRESS CATE 6 Compre ss 20 OPERATI0 1 WIDE MJL T I BAND CCl JTROLS M Mu l t i 12 00 Th is uni t 1s ge nera ll y rece i vers at the transmitter peak...

Page 61: ...M VAR W N Reverse Log Taper Right Turn Tr inme r Variable Wire Wound SEMICQ DUCTORS and INTEGRATED CIRCU ITS DIG DIP GE IC LIN ACC ADJ AL ALLM ASSY AX BKT BLK CQ ID Dig Ita l Dua l ln l ine Package Germanium Integrated Circuit Linear Accessories AdJUSt AIum i num A I umi num Assemb ly Axia l Lead Bracket Black Conductors EXT Externa l EXTR Extruded FEM Fema I e IN Inch IND Inductor INSUL Insulator...

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