User manual PIONEER SX-820 service manual

[. . . ] rilf , a EefvicecTlanual a sSx-37cIcI STEREO RECEIVER sx-8ecl ()rqoruErr MODELSX-3700 IN DISTINGUISHED FOLLOWS. 120V only '| 20V only 11OV 12OV , , 22OV , end 24OV(Switchabls) 11OV 12OV 22OV, and 240V (Switcha ) ble . , U. S. A. model Canda model Genral exDort model U. S. Military mod6l Ramarks KU KC e This servicemanual is applicableto the SX-3700/KU. [. . . ] 410 below consists of a Wheatstone bridge with the load RL forming one of the arms. Q3 is biased by the potential difference betyyeen diametrically opposite comers of the bridge circuit. If the RL value drops below a certain fixed level, Q3 will be tumed on due to forward biasing. The charge on C4 in the relay drive circuit will thus be discharged via D3 and Q3, resulting in Q6 being tumed off and the relay contacts being opened. If for any reason a DC voltage is generated at the output, it will be detected by the DC voltage detector circuit, resulting in the relay contacts being opened to thereby protect the speakers. Rb and C2 form a low-pass filter designed to block normal signal components, thereby preventing the application of signal voltages to the bases of Q4 and Q5. If a positive DC voltage appears at the output, it is divided by R5 and R6, and applied to Q4 and Q5. Since the base of Q5 is connected to ground, this transistor will remain off due to the reverse bias applied. And since the emitter of Q4 is connected to ground, this transistor will be tumed on due to a forward bias. Consequently, the base of Q6 is grounded by Q4, resulting in Q6 being turned off and the relay contacts being opened. If a negative DC voltage appears at the output, Q4 is tumed off due to a reverse bias, while Q5 is tumed on due to a forward bias. And since a negative voltage is applied to the emitter of Q5 in this situation, Q6 is tumed off and the relay contacts ooened. F|ly driv circuit F i g . 4 - 1 0 O v e r l o a d e t e c t o Ci r c u t D r i , l ""*";. ;;;l F Powr amplifir Overload detector circuit DC voltag dstsctor circuit l[&'#bfr ll J AC powor supply t:. | ;. + R6lay driv circuit I J 4, Fig. 4-11 Protection Circu it six-37ClCl 5. DISASSEMBLY Bonnet Case Remove the four screws O on each side of the bonnet case. Bottom Plate Remove the eleven screws bottom plate. O to detach the Front Panel Remove the all control knobs except push knobs. Remove the two screws tp and two nuts Q from the front panel. ?^ Bonnetcase Front panel ottom plate d Fig. 5-1 Disassembly -+-\? n 6. PARTS LOCATIONS Front Panel The [, mark found on some component parts indicates the importartce of the safety factor of the part. There' fore, when replacing, be sure to use parts of identical designation. Knob (TUNING) AAA065 Front panel assembly ANB-883 Bonnet case AMM89 Push knob AAD-226 Lever knob assembly AAD-139 Front View with Panel Removed F L assembly AWV-o12 Switch assembly GWS-233 Function switch assembly AWS-149 Lead out assembly AWVOl1 , lt, Switch (POWER) ASA-507 P h o n ej a c k ( P H O N E S ) AKN{30 V a r i a b l e r e s i s t o r( T O N E ) ACT-127 Switch V a r i a b l er e s i s t o r 5 O k ( V O L U M E ) 2 ACT-126 Switch (LOUDNESS) ASK. 157 Switch (MUTING) ASK-l59 V a r i a b l er e s i s t o r1 M ( B A L A N C E ) ACT{21 ASK. 157 sx-37clcl /';^ RearPanel Bar-antenna ssembly a ATB24 I AC soctet (Ac OUTLETS] AKP{39 tl^ Terminal(AM STEREOOUT) AKB{)76 Terminal (ANTENN AKAOl4 Pin iack I AC power cord ADG{23 v2 Terminal(SPEAKER) AKEO44 AKB{63 Top View /g^ Power amp/protector assembly GWM. 159 IPower transformer ATT696 Tuner/AF assembly GWM. 160 8^ J. ' D Detector assembly GWX463 n^ 15 7. Remove the bonnet case and front panel as described in the "Disassembly" section on page 1 2. Remove the tuning drum from the shaft of the tuning capacitor. Tie one end of the cord to the stud Q located inside the tuning drum. Rotate the tuning capacitor right around until the rotor blades are fully intermeshed. [. . . ] c204 c 2 0 9 , c 2 1 0 c 3 17 , C 3 1 8 c307, c308 c2t3, c214 c 2 1 5 , C 2 t 6 c20t , c208 c205, c206, c301 c304 c313 C316 c223, C224 SEMICONDUCTORS Symbol& O. scription rvt5214 L-P 2SA798 25C2291 25C2229 (25C1885) 2SC945A {2SC2575) 2SA949 (2SA912) 25C227 5A {25C1913) 2SA985A (2SA913) 2SC19144 2SC945A l2sc251sl 2SC1384 2SD880 (25D313) 2S8834 (2SB507) 2SD836A . i sR3AM4 . a1 o E 2 (srB01 2) 0 152472 (1S1 54) 5 o1, 02 03, 04 os, 06 07, 08 09, 010 o11, 012 o 1 3 , O r 4 o 1 5 , O 1 6 421 , 422 423, 424 425 017 ol8 019. O20 D1 D4 D16 D11-Dr3 33 Symbol& Dscriplion OTHERS Symbol & Description 152411 MZ-061 {w2, 061) MZ-150 (wz 150) MZ-270 MZ-130 {wz-130) (1S2473) KZLl)12 D14D15 , D17 D20 A KN{30 A K B, 063 AKE{44 vaz30Po60F Mc P i n j a c k4 P T e r m i n a l( S P E A K E R S ) Screw D 1 8 , D 1 9 D21 D5-D10 D22 1 O . P A C K I N G Oscript ion 1. 4. ADH{02 ARB-360 AHA-252 T-type FM antenna Operatinginstructions Side pad sx-3700 11 . E X P L O D E D I E W V Exterior Components ko / 10 e r, il Y 7 qt 8 6 t:--J , o-3 rs J g 13 14 15 (-i) f. 13 l - t I ;. t t5 r 13 NO?'t^Sl . [. . . ]