Realistic-STA720-rec-sm 电路图 维修手册.pdf

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1、ruLtstd. SerulceamuaI AM/FM STA-720 STEREOREGEIVER Catalog Number: 31-1997 L D cusloM MANUFACTURED FoR RADIo sHACKn ovstoN 0F TANDv coRpoRATtoN RadioFans.CN 收音机爱 好者资料库 CONTENTS 1. SPECIFICATIONS .3 function indicator des not light. A) Faulty AC power cord Replace the cord. B) Defect in the power swi

2、tch Replace the switch. C) Broken wire in the power transformer R ep lace the transformer. D) Blown power fuse F002 Replace the fuse. 2. Fr.rse blows when power is turned on.A) Power transformer T851 defective Replace the transformer. B) Short in the primary or secondary of the transformer circuitry

3、 Repair the short. C) Damaged rectifier D801 Replace the rectifier. D) Short circuit in the rectif ier circuit Repair the short. 3. Function indicator lights but no sound from both channels. A) SPEAKERS switch 510 or 511 defective Replace the defective switch(es). B) Defebt in transistors TR605a,b -

4、 TR60Ba,b of Main Amp Board #6079 Replace the defective transistor(s). 4. A speakers do not work.A) Speaker switch S10 defective Replace the switch. 5. B speakers do not work.A) Speaker switch S11 defective Replace the switch. 6. One channel does not work with VOLUME at maximum with a test signal ap

5、plied to the center terminal of VOLUME control VR902 of the dead channel. A) Defective 1C901 Replace 1C901 . B) Defect in transistbr TR601-TR610 of Main Amp Board #6079 Locate and correct the defect. C) Break in copper foil of printed circuit board #9046 or #6079 Repair or replace circuit board(s).

6、D) Short in speaker output terminal Repair the short. E) Defective resistor R901, R601, R603-R610, R615-R620 Replace the defective resistor(s). F) Defective capacitor C901, C601, C603 or C604 Replace the defective capacitor(s). 12 SYMPTOM CAUSE AND REMEDY 7. Same as (6) above but channel operates wh

7、en test signal is applied as in (6). A) Defective PHONO switch 52 or TAPE MON switch S7 Repair or replace the switch(es). B) Defective BALANCE control VR901 Replace. C) Resistor R910 defective Replace the resistor. B. Speaker works normally but headphone do not work. A) Headphone plug does not mate

8、with jack. Replace the plug. B) Defective resistor R651a,b Replace the resistor(s). 9. All inputs work normally except for AUX input. A) Poor contact in AUX input jack Repair or replace the jack. B) Faulty AUX switch S1 Repair or replace the switch. C) Defective resistor R510 Replace the resistor. 1

9、0. PHONO input not operativeA) Defective 1C501 Replace the lC. B) Faulty resistor R501, R503-R509 Replace the faulty resistor(s). C) Fau lty capacitor C501 -C503 Replace the faulty capacitor(s). D) Poor contact in PHONO input jack Repair or replace the jack. E) Faulty PHONO switch 52 Repair or repla

10、ce the switch. 11. TAPE MON not operativeDefective TAPE MON switch 57 Repair or replace the switch. Defective contact in TAPE lN jack(s) Repair or replace the jack(s). A) B) 12. FM does not operate.A) Short circuit in Tuner B+ circuit Repair the short. B) Defective FM(S4) or FM MUTE(S5) switch Repai

11、r or replace the switch(es). C) Resistor R219, R306, R317 or R318 defective Replace the defective resistor(s). D) Choke coil L201 defective Replace the coil. E) Capacitor C302 defective Replace the capacitor. F) Defective lC 1C201 or 1C301 Replace the defective lC(s). G) Defective I FT T101 Replace

12、lFT. 13 SYMPTOMCAUSE AND REMEDY H) DefectivetransistorTRl0l, TR102, TR103 or coil L101, L104 Replace the defective component(s). l) Faulty lead-in Repair the faulty lead-in. 13. Poor multiplex separationA) lmproper adjustment Readjust VR302 (refer to ALIGNMENT PROCEDURE on page g). B) Transistor TR3

13、02, TR303 or lC 1C301 of Tuner Board #OO74 defective Replace the defective component(s). C) Variable resistor VR301 or VR302 defective Replace the defective variable resistor(s). 14. Stereo indicator does not light.A) Defective indicator LED D406 Replace the LED. B) lmproper adjustment of VR301 of T

14、uner Board #0o74 Make readjustment. (Refer to MPX ALIGNMENT on page 9.) C) Defective lC 1C301 or resistor R426 Replace the defective component(s). 15. FM volume not sufficientA) lf volume of both L and R channels not enough: Front-End section defective, or faulty IFT T101 lC 1C201 or transistor TR20

15、1 of Tuner Board #0074 Locate and replace the defective component(s). B) lf sound of one channel not enough: Defective TR302 in case of L channel, or defective TR303 in case of R channel Replace the defective transistor. 16. AM does not operateA) Damaged 1C401 of Tuner Board #0074 Replace the lC. De

16、fective L4O1,T4O1,T4O2 or CF401 Replace the defective component(s). One of resistors of Tuner Board #0074 (AM section) defective Replace the defective resistor. One of capacitors of Tuner Board #0074 (AM section) defective Replace the defective capacitor. AM switch 53 defective Repair or replace the

17、 switch. Defective Tuning gang capacitor Repair or replace. Damaged AM Bar antenna Repair or replace bar antenna. B) c) D) E) F) G) 14 SYMPTOMCAUSE AND REMEDY 17 . LOUDN ESS has no effect.A) Defective LOUDNESS switch 59 Replace the switch. B) Defective capacitor C91 1, C912 or resistor R91 1 Replace

18、 the defective component(s). C) Defective VOLUME control VR902 Replace. 18. Stereo-Mono not effectiveA) Defective MONO switch 58 Replace the switch. 19. TAPE MONitor not effectiveA) Defective TAPE MON switch 57 Replace the switch. B) Poor contact in TAPE MON lN jacks Repair or replace the jack(s). 2

19、0. BASS control has no effect.A) B) BASS control VR903 defective Replace. Defective capacitor C903, C904 or resistor R915, R917 Replace the defective component(s). 21. TREBLE control has no effect.A) TREBLE control VR904 defective Replace. B) Defective capacitor C905-C907 or resistor R918, R919 Repl

20、ace the defective component(s). 22. Excessive noise with PHONO inputA) Faulty 1C501 Replace the lC. B) Faulty R501-R504, C501 or C506 Replace the faulty component(s). 23. Noisy VOLUME controlA) Defective VOLUME control VR902 Replace the variable resitor. B) Defective capacitor C503, C901, C908 or C6

21、01 R ep lace the defective capacitor( s). 24. SIGNAL STRENGTH indicator LED not functioning A) Defective LED D401-D405 or lC4O2 Replace the defective component(s). B) ln case of FM reception, VR201 or D2O2 defective Replace the defective component(s). C) ln case of AM reception, 1C401 or R416 defect

22、ive Replace the defective component(s). 25. AUTO-Magic AFC has no effect when AUTO-M switch is ON. A) Defective D 101, R 1 18, R22O or C213 Replace the defective component(s). 15 SYMPTOMCAUSE AND REMEDY 26. Frequency counter LED does not light when FM or FM MUTE button is pressed in. A) Diode D803 d

23、efective Replace the diode. B) Capacitor C701, C704, C810 Replace the defective capacitor(s). 27. Frequency counter misreads in AM or FM reception. A) Defective crystal XR701 Replace the crystal. B) Defective lC 1C701 or transistor TR702-TR705 Replace the defective component(s). 28. Frequency counte

24、r misreads in only AM reception. A) Defective AM switch 53 Replace the switch. NOTES 1. This Receiver have two built-in over load thermal protection for abnormaloperation. When the temper- ature of thermal protector one is installed with heat sink (S14, 105C) and the other with power transformer (S1

25、3, 90C) does rise abnormally (105 t 5C or 90 + 5oC), the thermal protector will automatically cut out, and as soon as the temperature goes down sufficiently (35 t t5C), the ther.mal protector turns back-on automatical ly. lf the Receiver does turn itself off, check ventilation and speaker connection

26、s. HEAT SINK Ft)R POWER POWER TRANSISTORS TRANSFOEIVIEB 2. Transistors TR609 and TR610 protect audio output stage when abnormally high current flows in TR607 and TR608 due to excessive input drive, or a too low impedance load connected at output. TR609 and TR610 are not normally biased on and collec

27、tors of thesetransistors (through D603and D604 diodes) reduce biases on TR605 and TR606. This decreases drive to output transistorsTR60T and TR608 to reduce the current. This occurs not only to protect the circuit but also the speakers against high level switching clicks and pop noises. AC I2OV 60Hz

28、 +Vcc F =a E - E o o F TH E R I4AL PROTECTO R OOT4.TUNER BOARD (TOP VIEW 17 OO74 TUNER BOARD (BOTTOM VIEW 18 6079 MAIN AMP BOARD (TOP VIEW) t- & f 19 6079 MAIN AMP BOARD (BOTTOM VIEW) -J J I 20 7225 FREOUENCY COUNTER BOARD ffOP VIEW) 7225 FREOUENCY COUNTER BOARD (BOTTOM VIEW) 21 7226 SWITCH BOARD (T

29、OP VIEW) 52 SI 53 54 55 7226 SWITCH BOARD (BOTTOM VIEWI 22 8044 POWER SUPPLY BOARD (TOP VIEW 8044 POWER SUPPLY BOARD (BOTTOM VIEWI (a)* Star (*) marked components are used in Canadian models only. 23 9046 TONE (TOP VIEW CONTROLBOARD (BOTTOM VIEW 24 SEMICONDUCTOR LEAD IDENTIFICATIONS 25 CAPACITORS Re

30、f . No. Value (F) R/S Part No. Voltage (v) Toler- a nce %t Material c101 c102 c1 03 c 104 cl 05 c1 06 c1 07 c 108 c 109 cI 10 c111 c112 c1 13 c114 c1 15 c1 16 c117 cI 1B ct 19 cl20 c121 c122 c123 c 151 c201 c202 c203 c204 c205 c206 c207 C2OB c209 c210 c211 c212 c213 c214 c215 15p 0.0221t 0.022p 0.02

31、2p 0.022rt l Bp (sH) lop Not Used 220p 0.022p 0.022p o.5p 0.01p 2p 12p 15p lop 33p(UJ) 15p Not Used 0.022p 0.047p 0.47 p lop 0.022p 0.01p 0.047p 0.022p 0.022p 0.0471t Not Used 1 00p 0.022p 0.47 p lop 4.47 p 33p 0.022p 0.022p F.728 cF-1226 c F-1 902 cF-1 100 cF-1425 50 25 25 25 25 50 50 50 25 25 50 2

32、5 50 50 50 50 50 50 25 25 50 16 25 25 25 25 25 25 50 25 50 16 50 6.3 25 25 tl0 +80 -20 +80 _20 t0.25p F +BO _20 t0.25p F t0.25p F t10 t10 r10 t10 t10 +80 -20 +80 -20 +80 -20 +80 -20 t10 tl0 +80 -20 +80 -20 -lo +50 -10 +80 -20 +80 -20 +80 -20 +80 -20 +80 -20 +80 -20 t10 +80 -20 +75 -10 +50 -10 x20 t2

33、0 +80 -20 +80 -20 Ceramic Ceramic Ceramic Ceramic , Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Electrolytic Electrolytic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Electrolytic Electrolytic Elec

34、trolytic Electrolytic Ceramic Ceramic Ref. No. Value (F) R/S Part No. Voltage (v) Toler- ance (%) Material c216 c217 c21B c219 c220 c221 c301 c302 c303 c304 c305 c306 c307 c308 c309 c310 c31 1 *c312 *c313 c314 c31 5 c31 6 c317 c31 I c319 c320 c321 c401 c402 c403 c404 c405 c406 c407 C4OB c409 c4l0 c4

35、11 c412 0.022tt 0.0221t 0.022p 1op 0.022p 1p 10rr 1 000p 0.47 p 0.47 p 1 500p 0.47 p 0.22p 0.22p 0.047 p 4700p 4700p 3300p 3300p 1 000p 1 000p 0.056p 0.056rr 1Bp 18p 1p 1p 0.0 1p 10rr 0.047p 1 000p 0.0lp 0.01p 68p Not Used 47p 0.01rr 0.022p 0.01rr cF-1914 cF-1914 c F-1 959 cF-1 366 25 25 25 16 25 50

36、 16 16 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 50 25 16 25 50 50 25 50 50 25 25 25 +80 -20 +80 -20 +80 20 +50 -10 +80 -20 t20 +50 -10 +50 -10 +75 -10 +75 -1 0 t10 t20 t,20 t20 t10 tl0 tl0 t10 tl0 t10 t10 t10 t10 tl0 t10 t20 t20 +80 -20 +50 -10 +80 -20 tl0 t10 +8O -20 t10 t10 +80 -20 +8

37、0 -20 +80 -20 Ceramic Ceramic Ceramic Electrolytic Ceramic Electrolytic Electrolytic Electrolytic Electrolytic Electrolytic Polystyrene Electrolytic Electrolytic Electrolytic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Electrolytic Electrolytic Ceramic El

38、ectrolytic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic *C312, C313: 12OOp for European/Australian models 26 Ref. No. Value (F) R/S Part No. Voltage (v) Toler- ance (%l Material c41 3 c414 c41 5 c416 c417 c41 I c419 c420 c421 c422 c423 c424 c425 c426 c427 c428 c429 c45 1 C

39、501a,b C502a,b C503a,b C504a,b C505a,b C506a,b c507 c508 c509 c51 0 C51 1a,b C601a,b C602a,b C603a,b C604a,b C605a,b C606a,b C607a,b C608a,b C609a,b 0.01p 4.7 p 1p 1 000p 0.01p 2200p 0.47 p 1 00p 0.022tt 47p 0.022p 1p 10rr 0.047s 8p(uJ) 1 00p 4.047 p 8p 4.7 p 1 00p 2.2p 1 800p 8200p lop 0.047p 0.047

40、 p 0.047 p 0.047p 200p 1p 220p lop 47p 1op 6p 33p 1 000p 1 80p 251t-14c cF-t I I 25 25 50 50 25 50 50 r6 25 50 25 50 16 25 50 50 25 50 25 50 50 50 50 16 25 25 25 25 50 50 50 50 50 500 50 16 50 500 +75 -10 tl0 x20 +50 -10 t0.25p F t0.25pF +50 -10 t10 tl0 +80 -20 +75 -10 +75 -10 tl0 +80 -20 r10 +75 -1

41、0 +50 -1 0 +80 _20 tl0 +80 -20 +75 -10 +50 -1 0 +80 -20 t5 t10 +8O -20 t5 +75 -1 0 tI0 +50 -1 0 t10 t10 +50 -1 0 +80 -20 +8O -20 +80 -20 +80 -20 tl0 Ceramic Electrolytic Electrolytic Ceramic Ceramic Ceramic Electrolytic Electrolytic Ceramic Ceramic Ceramic Electrolytic Electrolytic Ceramic Ceramic C

42、eramic Ceramic Ceramic Electrolytic Ceramic Electrolytic Polyester Polyester Electrolytic Ceramic Ceramic Ceramic Ceramic Ceramic Electrolytic Ceramic Electrolytic Electrolytic Ceramic Ceramic Electrolytic Ceramic Ceramic Ref. No. Value (F) B/S Part No. Voltage (v) Toler- ance (/rl Material C610a,b

43、C61 1a,b C612a,b C613a,b C614a,b C615a,b CG 1 6a,b C617a,b C65 1a,b c701 c702 c703 c704 c705 c706 c707 c70B c709 c71 0 c7 11 c712 c71 3 c7 14 c715 c71 6 c7 11 c71B c719 c720 c721 c722 c723 c801 c802 c80s cB04 c805 c806 c807 c808 c809 Not Used 1 00p 1 000p 33rr 1 80p 1 000p 1 000p o.1p 1 000p 0.04rr

44、1 00p 2200p 470p 47p 2op 2200p 0.04p 470p 2200p 2200p 2200p | 2200p I | 2200n | 2200n 2200p I | 2200n I az00n 1 47000 I | +700n I 4700p I I t0000 | 1000n | 0.01rr | 0.01pr | 0.01p I o.oru I I a700r | +zoou I 47u | ,ru I rou cF-l811 cF-l811 cF-l811 cF-l811 cF-149t cF-149( ,r,11 ,t ,rrl )F-1425 50 50

45、25 500 50 50 50 50 25 50 25 6.3 50 50 50 25 6.3 25 25 25 25 25 25 25 25 50 50 50 50 50 50 I uoo I u,o I 500 I uoo t40 loo l,u lru II ro tl0 tl0 +50 -10 t10 t10 t10 tl0 tl0 +80 -20 t10 t20 t20 t10 tl0 t10 +80 -20 t,20 x20 x20 x20 t20 t20 t.20 t,20 t,20 x20 t,20 t,20 t.20 tl0 x20 +1 00 -0 +1 00 -o +1

46、OO -o +1 00 -o +50 -1 0 +50 -1 0 +50 -10 +50 -1 0 +50 -1 0 Ceramic Ceramic Electrolytic Ceramic Ceramic Ceramic Polyester Ceramic Ceramic Ceramic Ceramic Electrolytic Ceramic Ceramic Ceramic Ceramic Electrolytic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic

47、Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Ceramic Electrolytic Electrolylic Electrolytic Electrolytic Electrolytic 27 Ref. No. Value (F) R/S Part No. Voltage (v) Toler- an ce %t Material c810 c81 1 cB12 C901 a,b C902a,b C903a,b C904a,b C905a,b C906a,b C907a,b C908a,b C9 09a, h C910a,b C91 1a,b

48、 C912a,b 2200p 1 000p 0.01p 1p 1p 0.022p 0.068p 0.018p 1 80p 6800p 1op 1p 1p 0.068rr 120p cF-1470 6.3 50 25 50 50 50 50 50 50 50 16 50 50 50 50 +50 -10 t10 +80 -20 +75 -10 +75 -10 110 t10 t10 t10 t10 +50 -10 +75 -10 +75 -10 tl0 i10 Electrolytic Ceramic Ceramic Electrolytic Electrolytic Polyester Pol

49、yester Polyester Ceramic Pol yester Electrolytic Electrolytic Electrolytic Polyester Ceramic COILS & TRANSFORMERS Ref. No,Description R/S Part No. Mfrs Part No. 1101 Lt 02 L1 03 Ll 04 L201 L202 1401 145 1 T1 0r T401 r402 L601a,b 170 1 LBOI T851 T85 1 T85r T85 1 T201 r202 FMAnt. Coil 133A FM RF Coil 1408 Choke Coil 2.2mH FM OSC Coit 122L Choke Coil 2.2mH Choke Coil 18pH AM IFT Coil4l6L AM Ant. Coil FM IFT Coil 209A FM Det. Coil 230D FM Det. Coil 231D AM IFT Coil4074 AM IFT Coil 407B Choke Coil l.5pH Choke Coil 33pH Chokri Coil 33pH Power Transformer(U L) Power