SERVICE MANUAL FOR
Contents
1. 2215 APf INYIY8 gRDB E lt Ss E lt 820 T 270K S Ly i d N D2f6 D21 o E N E qx INFINE tv 6 8v G t cetme7 X VS a N f00n e ov Rea T 101 ctor EE y P 120VA weii sss Sec Qx25V QN H amp c D22 MDA 970 2 lt t e e E s wu RBLS e fof BY225 200 3 a lt E O02 3 D218 7S SOK Gem e jad 3 CD4001AF W4f48 H prak psoz 220 e 0y OAT POV v w D Je CS veer COMET x 110 1207 2 0AT 1 0V ag UA Gn 250v enz Gg 90 00v ES GER R 504 3 3m 10 Ov CsotkP C500 EP a AF 4 D201 8 3 RSO e SH 684 BS Rs02 Kal E A AL EES E fn S R Os amp SIPE Le ov R5 C507 Cer se Kee Ka DT 25 1003 wies 63v PSIO fk fer Ly 2 BK 150p Treble L602 Q O 56m H 66 A MIDRANGE AND TREBLE SECTION S E we kb CA ew ss 1331 o RIME 18k WS e Ym B PWALIPS o XO EADSoeft P s ov ton 250v Cader core Se CB mer k Un gSoV I T Wn 63v 2 400X Or T7OS BC546B C AO e r de C 09 100p j Go C a 8 amp i LA SIPE AS 120 42148 1 035 R305 S f 24k C303 mec AC CHECKPOINTS mv blend 68n Rov SENSITIVITY in max BASS and TREBLE in mid positions Adjust input tor H mV nt Orivers ec ec n porn d conn BOW 948 C 708 eh Ze Ow 46 C 708 100 Point SO Hz SOHz 1k Hz 2 SkHz iOk Hz Ge2. crossover filters L602 C616 C617 to midrange and C614 C615 and L601 to the tweeter 2 FAULT FINDING A4 14 does not works Set auto ON OFF in position ON Check that both the green and red LED are lit Check the power fuses and fuses F601 602 701 and 702 Measure supply voltages 33V 2 5 33V 2 5V 15V 2V 15V t2V To localize the fault connect test instruments as follows Tone generator to J301 pins 3 and 5 Adjust till B is 42mV Sensitivity in Max position bass and treble pots in center position Compare to voltage levels according to tayle in circuit diagram If fuses F601 602 702 blow during measurement per Section 1 4 you may disconnect the woofers and replace midrange driver and tweeter by 5 10 ohm resistors Test again per Section 1 4 signal levels in points E F G K and J will of course be different Auto ON OFF can also be tested with set up per 1 4 Set auto ON OFF in AUTO The signal at 2201 pin 1 should be 7V p p and the signal 2201 pin 7 should be 15V DC Relay K101 should close at 15mV 500 Hz in R210 may be shunted by 100 kohm to reduce the off delay wp07029 3 ADJUSTMENT 3 1 Bias current in power amplifiers After replacing any output transistor in any of the power amplifiers the bias current must be readjusted Setting of bias current should be done while heatsinks are at room temperature that is immediately after A4 14 is turned on Set potentiometer R722 o
3. 7 0V 7V Z201 5 6 7 plus transistor V201 works as a schmidt trigger with ON level approx 7V and OFF level approx 5V The input pin 5 senses a DC voltage which is obtained via diode D211 and capacitor C206 Transistor V201 drives relay K101 which connects power to the audio circuits in A4 14 When switch S201 is in AUTO position relay K101 will open about 5 minutes after the signal at the input disappeared The time relay is determined by C206 and R210 During test you may shunt R210 by 100 kohm to obtain shorter OFF delay wp07029 3 When switch S201 is in ON position the auto ON OFF circuits are bypassed and A4 14 remains permanently ON A thermistor TS3 75 senses the temperature of the heatsink When this temperature is too high the thermistor resistance becomes so low that relay K101 opens 1 3 Overload protection for midrange and tweeter 2202 4 13 acts as an overload protection device which is actuated if there is risk for damage to the midrange driver or the tweeter The voltage across the voice coils are rectified in diodes D220 and D219 and the rectified voltages charge capacitors C211 and C212 The time constants for discharge are longer than the charging time constants If the voltage at Z202 pins 5 or 6 exceeds a threshold value approx 3 4V the monostable flip flop Z202 8 13 is triggered for 10 seconds This causes V201 to be shut off so relay K101 opens and A4 14 is deenergized for 10 secon
4. E A nv vem mt Om lou PELI de ati n p CISMAI cuse POP Iov xcd i T 10 63y 2AF POWER AMPLIFIER BASS s j meT me t polyester 55 EA T ACE Bass cirevit Enclosure 5 3 0 3W 2W L WW 2 1 sx Sieste as s electrolyte Adjust R410 for 3 5 9B flower vel af Fe MOT T E Farra lore 180 3 Mz Compared to 6OT Wz inpont 4404t sev Table oec i 7 DIJ T E EUM Bass mers box musi be connecte el wie det 1 osw D fw SE mec ai Cer Ceramic 2 2p eege i 5 ee IT T ERE i br pla LL AAOS en d naiai ef those shaolta AUXOR AB MOTALA SWEDEN POWER SUPPLY D219 MIDRANGE TWEETER p ets R26 IN 9158 R224 I si Em T L ZE 820 e 270K E sha N D216 D217 Q QN Ov 6 8v G8v ceIomeT UO s e 430v N f00n 2 sov S gt i R219 CR vo c o ceo oe R103 ziot P Ser edou wn f0n 250v Eu BENE P 120VA k 0f S x Ge AK S DS Sec 2x25V amp J A a amp js Dlo oy ee R d D220 n 1 049 0 2 Red De lose 22k SR te ES gt s IN41 8 R225 20 938 F fof PY225 200 tt ctos 3 n D218 gt Bow 4o oh S x K6L02 ON 700m V fO 63r SS 3455 3x CD5001A 4158 M E yom t cto6t BC 556 B 20 240y LorTl2e2ov S q 4 Tao bIr p COMET 10 129Y 20AT 110V SSS SH ph 100 100 6 844 10 100 eto x a RIOS 22k i i FOR X X SNS lt D ex T603 cusmer STA lt l eer er S 7602 B
5. LF 94 eer TLO Y 8 fy SA a M la tof 1X 7707 A s en a SS LI Ga _ Ah S PIIf ml 2 EE sl lz IR Ke EE 0 15 mv YIK lin LP LINK AASV Cape oe x lt E u Bass gt R S lt Thermo aC Ras 2x SIPE AS i d RS SE eU Cou lec ub IS lt KJ gt 30 4214B 1 03 lo 255v amp z io el LIES af i C716 mec R4OS n 0r 250v P e lt A n r 3X A Ac Geer mV ce mer P ga afi SENSITIVITY in max BASS ane TREBLE 17 0684 Ov Jal jo 25 ilo mid positions Adjust input Yor SR mv yen oN i w LN a w 9 fed in point E Privers connec ec BOw 948 C708 Ze Lee Q amp RYO C 208 700 SO Hz 250Hz 1kHz 2 5kHzljokHz 8 P v 0 t1i o A om rem EE mr 33 B i Y n 50v pete ea Te 3 7 a lt o es ve pr 63 e e 8 e e 1 g s 730 2 eee FON GEES 930 2 40 DES d 53 amp o 65 0 5 W a 0 e 1 us e 7 D 200 ato ze 35 T met wel polyester 55 TEN BT E77 sso o 3 2w ree L i 2 1 Slo mF s foly propylene EC lecfrolyfc SE sy T Tifantalum c o 3w Zb l MEC BlicartonareS id Cer liane i 2 E f vat l l 5 s T vi CS POWER AMPLIFIER C o mer fOOn e5ov ACE Bass cirevi Adjust Raso Sec ZZ ed lower level at 1601 3 Mz compared de 602s Hz impont G Lass driers m box must be corrected BOWL x lt TOLERANSER OM J ANNAT RA A
6. NGIVET UNLESS Se n CIISMET CHSE We 3ov aca li T 10m 63V POWER AMPLIFIER BASS Enclosures 5 5 E MM MEE HGO MATEMAL YYOC Sage Gem CHE i CIRCUIT DIAGRAM L 44 4Mk3 mtu S on naive nro Ri A AMI Any infringement tssion thout our permi in part wi This document must not be copied either completely or in Material ordered with reference to this specification shall in every respect meet the requirements and data Denna handling f r ej utan v rt medgivande delges annan kopieras eller eljest obeh rigen anvandas ef 3 2 ul ve kMonferas upplyf tade fr n 9 kortet st motst nd xinstall at distanse from card 10 resistors e R410 R617 R722 lises med E E Mie T och with varnish after i adjustment Limmas med 3140 3 E C701 C702 mont tad och bockade SE EENG 771 H PT gt k ITL0ZZCN yec TL082 CP CD4001A BC546B EE i BL 556 B e i Uppgiord f r Project d e c A4 14 Botten v dio ue CAO Scale Ritrungsnummer Drawing nr arron wey E Leen ZZ ebe 1 1 3 141504 i X fugal oO XC 828 V ABDA
7. REVISION 3 1992 04 02 audio pro SERVICE MANUAL FOR A4 14 A4 14Mk2 A4 14Mk3 Address Phone Fax Telex Audio Pro AB Nat 0370 717 08 Nat 0370 762 55 40467 Box 65 int 46 370 717 08 Int 46 370 762 55 FLINTAB S 568 22 SKILLINGARYD SWEDEN LIST OF CONTENTS wp07029 Page TECHNICAL DESCRIPTION Li e aan 2 1 1 Power Supply Circuits Lera ida 2 1 2 Automatic ON OFF TRU 2 1 3 Overload protection for midrange and tweeter 3 1 4 Signal Amplifier Circuits ba verano a 1 5 Bass CLOUT CS doa Oda ex i e e e e e e s 9 9 e e e 9 e A 1 6 ACE Bass GB ei ei AB ei L Q dro ate podes va d iu 4 1 7 Midrange and treble circuits 5 1 8 Power stage for woofers 5 1 9 Power amplifier for midrange and tweeter 6 FAULT FINDING ee oe eee Eeer P eel et THES 6 ADJUSTMENT e e e 9 o e e 9 9 9 e e e 9 ss 9 9 e e a e e e o9 e 7 3 1 Bias current in power amplifiers 7 3 2 Negative output resistance 7 SPARE PARTS o Gebo i iu S ORES ent 7 ENCLOSURES 5 1 Circuit diagram 2 141502 A4 14 S N through 12399 5 2 Component layout 3 141504 A4 14 S N through 12399 5 3 Circuit diagram 5520991 01 A4 14 Mk2 S N from 13499 5 4 Component layout 4 80150 A4 14 Mk2 S N from 13400 5 5 Circuit diagram 1 80226 A4 14 Mk3 S N from 0100 1 TECHNICAL DESCRIPTION The descriptio
8. c556B 33 10 poy v TE Keier 5 O BCSS6B a K tad O O ur o BEE SCH Q ch re b E PS ee S ae tee I ceu a inne eer 3 AS 16013 D201 D202 ee d SE N Ders k 1N4004 NI 1N4004 IN 400 S ls q AUTO TURN ON IE ip eme SIPE c503 R506 c507Cer Ky DT 25 1003 C201 Ee CG N 200 680p 630V 63 P510 EI a res 352 50 Treble SI x 0 Aw P 602 1004 fV H 68K re ids Ss T 8 ow 46 R UN N O 56mHO6n2 D206 43 Green ff MIORANGE AND TREBLE SECTION x8 x AUTO x us di d pao 202 8 Sal T E 1205 AC 2x IN4 48 ex 1N4Y148 Za Za DN x era N D2o DESS Se Det 1339 97 um a PHILIPS C POP T C o T elis 1041468 A Thermally connected amp 9 L Ap 50600 d E gt 330n 00Y ES 4344 15V fo hentsm C604 MET F602 dov QV r 400n 250V C fOomkc c612 PAF c6f8 mer IV D208 gt L 0n 2 50V a F Op 63v 2 2p440 0 D2fO ipsc a a ee a RR UR MMC DE R6IE 18k 2x1N 4148 6 BV E RE08 4 f c 204 cr L c2os T 4x IN41 48 T705 BC5468 22 fOv S 2 f00 250v Do 2AF c 203 m 100K divit O 470905 SE y D S Y T 2 0 ep Pr AF774 15y c ot E 20 738 C708 67p5 A KA BOW 4 c 708 100p 1001 log X SC LEIN 8 zi Q pa M a TL O74 OW 00 MET R302 R303 9 LIS TRS n 100v AM C308mrT IN o S a SS N eed ind af UO y BERN tak 12k fo 2 Pani Sla a 3 D711 amp 3o2 EP pAF 774 eg m CODE R403 x 1N4148 N a 680p 630v
9. d component number per circuit diagram 2 141504 5520991 01 resp 1 80226 wp07023 G i Ab T ithe rx E 1 3 di Oh fm M ba I zT Sal m db SS e BO Eat Le _ l Ed Enclosure 5 4 Benimning Description Ben mning Description Material Detalj eje LU pus L T KN n Mauclo pro SWEDEN Ritn nr Org No 4 80150 P P izova C OWer Supply Sec 2x25WVq T 101 D217 K 101 6 8V F101 MDA970 2 BY225 200 KBL 02 1 0 AT 220V 2 0 AT 110V 34 CD4001AE or in pert without our permission Any infringement This document must not be copied either completely wit lead to legat proceedings 110 120 V 220 240 V C202 47M 0 33 p D211 C2061 T 1N4148 ppl 0208 em 47y f ETE 63V w i T ame e R208 AN C205 2cpsco1ae 0 18 R205 100 K C203 47n S Sensitivit R306 y B shall in every respect meet the requrements and data Material ordered with reference to this specification stated beem 911c301 p yAFT74 YT fex R307 LF347 315 pAF774 RAO R302 R30 18K 16074 veel pen C304 6 4K EU 12K i3 14 4 I d SE 2307 SL reng 0 475 Ot A An LF347 R309 R340 R316 2 pAF774 sox 82K umm R305 R311 a 47K 2 D 24K tin LP link HP filter 919 c3o3 Bass 68n AC checkpoints SENSIVITY in max BASS and TREBLE in mid positions Adjust input for 42 mV in poi
10. ds 1 4 Signal amplifier circuits When the Bass Blend switch is OFF the signals enter via R302 C302 and R303 When the Bass Blend switch is ON the bass frequency signals in left and right channels are added via filters C301 R301 R304 C303 and R305 C301 and R301 is a high pass filter with cutoff frequency 100 Hz Lower frequencies are attenuated by a factor of 2 R304 C303 and R305 is a low pass filter with cutoff frequency 100 Hz and attenuation 1 2 relative filter R302 C302 and R303 The signals below 100 Hz are summed at Z301 pin 9 Because of the attenuation introduced in each channel the bass level is the same as when Bass Blend is not used The gain is adjusted by potentiometer R306 in the feedback circuit of operational amplifier number one After this amplification the signals are split to bass circuits and midrange tweeter circuits 1 5 Bass circuits The signal passes the bass control circuits R311 Z301 12 13 14 which controls the signal level to the woofers The bass control circuits affect higher frequencies e g 100 hz more than low frequencies e g 30 Hz The bass signal then passes via a low pass link R313 C306 which forms one part of the crossover filter between bass and midrange The next link is a high pass filter which cuts frequencies below 30 hz 12dB octave and is part of the woofer s total transfer function 1 06 ACE BASS Circuit The power amplifier for the woofer t
11. n below applies to types A4 14 and A4 14Mk2 For type A4 14MK3 the DIN connectors have been replaced by RCA connectors and the BASS BLEND LEFT RIGHT and AUTO ON switches have been deleted but other functions still apply 1 1 Power supply circuits Unregulated voltages 30V and 30V supply the Power Amplifier and also a regulator for 15V 15V supply tracks 15V in order to avoid transients and oscillations when power is switched on or off The positive supply must decay faster than the negative supply when power is disconnected which is assured by a 2 2 kohm dummy load R101 on the 30V capacitor 1 2 Automatic ON OFF The auto ON OFF circuits are powered via D201 D202 and C201 The power transformers and the auto ON OFF circuits are powered as long as the speaker A4 14 is plugged in to a live outlet The remaining circuits are powered only in ON state when relay K101 is closed The audio signals enter via pins 3 and 5 in DIN connector J301 The other A4 14 in a stereo pair receives signals via pins 3 and 5 in DIN connector J302 The signals enter the amplifier circuits via pushbutton switches 301 S302 which select Left or Right Channel The input stage of auto ON OFF Z202 1 2 3 works as amplifier with gain 7 determined by feedback network R204 and R205 D208 and D209 limit the amplifier signal to 7V The second stage Z201 1 2 3 works as amplifier with gain 2 000 at 500 Hz The signal at pin 1 is limited to
12. nt B Drivers connected a p L eh 45eV Gate 3aY _ mV 0 Y Polypropylene or 4 dae capacitor 370aV PX hett EE V A 0219 mares ven Power Ampli ier Midrange Tweeter R220 1C211 R222 s 330K 68v 15M ER 63v R219 C210 T D220 1N4148 R22S 184148 C212 Ex R221 15M LA C614 C501 6 8y Pe C615 K e Thermo 33 SER coupled 15mv SIPE 1 p K 07251003 C616 C617 Ne Midrange and Treble section C610 C612 Te T top 8C5568 R612 18K imA SmA vr aama n 4x1N446 7 ve VIX 805468 30v Power Amlifier tas ee Bass v710 80w 938 e Bow 41 3x1N 4148 Gagn 701 0703 0705 1 2x SIPE AS 13042148 1 035 7 vt e 1W lt 50mV G I nemo 10 couple Mid R725 3x 14148 je C716 g D702 D704 D706 ton P 8DW945 8DW46 F702 R409 a am C713 C715 2af 30V SERE v7o9 Rao Ran BCS568 Jom Hios eav CIC al pra LF353 i TL062 Uppgjord f r Project Audio pro A4 14 MIDITACE 2 141502 ACE Bass circuit Adjust R410 for 73d8 lower level at 180 3 Hz compared to 60 1Hz in point Bass drivers in box must be connected nr Enclosure 5 1 nda amp A w n A ae lo deit POWER AMPLIFIER POWER SUPPLY Dery MIDRANGE TWEETER 2 GENE Qi sane M sun tants
13. ogether with 2302 1 2 3 5 6 7 forms the ACE BASS amplifier which can be represented by the diagram below Re R I GUin R412 and Z302 1 2 3 sense the voice coil current in the woofers 2302 5 6 7 acts as a band pass filter and sums signals from D and F The power amplifier for the woofer is inverting and acts as adder for signals from E and F The part of the current signal F which is fed back positively produces the negative output resistance R The parallel resonant circuit Lp Rp Cp is formed by negative feedback of the current signal via the band pass filter ACE BASS Amplifier Controlled Euphonic Bass wp07029 1 7 Midrange and treble circuits From the gain control the signal is also fed to the midrange treble amplifier Z301 5 6 7 acts both as high pass filter for the crossover C502 R501 R502 and as treble boost filter R505 R506 C503 The high pass link C504 R507 R508 forms the second part of the crossover filter between bass and midrange The power amplifier is of the inverting type and acts as operational amplifier for the treble control R510 which is active above 5kHz 1 8 Power stage for woofers The signal is coupled via C703 to the input of the power amplifier From the output the signal is fed back negatively via R709 and C704 When the signal amplitudes are large negative feedback also is provided via a network of resistors and diodes The output signal is c
14. ompared to the supply voltage and a couple of volts before clipping will occur the signal will be rounded by the diode network so the clipping is soft The input stage consists of a differential stage V702 and V707 fed via a constant current generator V701 The output stage is of Darlington design with transistors V710 V711 and has AC gain 1 V707 senses the temperature of the output transistors so that the bias current is constant V705 and V709 filter the supply voltage for the input stage eliminating hum and other kinds of noise If A4 14 pops when switched on one of these transistors is probably shorted No signal DC levels of voltages and currents are shown in the circuit diagram enclosed To avoid on and off transients the bass amplifier is active only when the supply voltages exceed 17V so that the operational amplifiers always work properly when the bass amplifier is active When diode D712 starts conducting the constant current generator V701 starts working and via V712 activates the current generator V706 The amplifier is inactive when these current generators are shut off wp07029 ean 6 sun 1 9 Power amplifier for midrange and tweeter The power amplifier is similar to the bass amplifier but the diode network for soft clipping is not included The voltage delayed on function is also eliminated so this power amplifier is active at low supply voltages The signal from the power amplifier is split in passive
15. r R617 till DC voltage between emitters of V710 V711 reads 10mV or voltage between V610 V611 reads of 20mV which corresponds to 23mA bias current NOTE When output transistors are replaced heat sink compound must be applied to both sides of the insulations washers and to the temperature compensating transistors Check that insulation is adequate and that the power transistors are mounted flat against the heatsink The heatsink must be screwed on to the PC card before the transistors are soldered in 3 2 Negative output resistance After replacing a woofer or any of the current sensing resistors R408 R412 the negative output resistance must be re adjusted The woofers must be properly mounted in the cabinet their voice coils must be connected and the bass adjustment potentiometer R311 must be in centre position Voice coils must be cold at room temperature Apply an input signal of 60Hz 1 Hz and adjust signal generator till test point G reads OdB 775V Change frequency to 180 Hz 3 Hz without changing the signal level of the signal generator and set potentiometer R410 till voltage at test point G is 5 5dB 5 5dB below 60 Hz Go back and forth between 60 Hz and 180 Hz and readjust if required until the difference is stable at 5 44 4 SPARE PARTS Spare parts can be obtained from Audio Pro Sweden or from Distributors and Service Centres When ordering spare parts please refer to serial number of speaker an
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