Trace_elliot_velocette12r 电路图 维修原理图.pdf

TRACE ELLIOT SERVICE MANUAL NO. SM00025 ISSUE 1 Date:January 6, 1997 Product Code :T3455/3456 Model No :Velocette 12R / Alnico Technical File No :TE00025 Issued by: Trace Elliot Limited. Blackwater Trading Estate The Causeway, Maldon Essex CM4 4GG. 收音机爱好者资料库 Ra d i o Fa n s .CN 收音机爱好者资料库 Ra d i o Fa n s .CN 收音机爱好者资料库 Ra d i o Fa n s .CN 1 C32-PCB-PC00064x3. VELOCETTE 12R ISSUE 3 14/2/97 PS DescriptionPart CodeQtyWhere Used PCBPC00064 issue 11 RESISTORS 0 ohm link72-RCZERO1R37 2R7 1/4W72-RM2R72R80 R81 10R 1/4W72-RM10R2R48 R49 56R 1/4W72-RM56R1R55 82R 1/4W72-RM82R1R47 1K0 1/4W72-RM1K4R27 R50 R51 R57 1K2 1/4W72-RM1K21R14 1K5 1/4W72-RM1K55R2R7R10 R22 R23 4K7 1/4W72-RM4K71R46 10K 1/4W72-RM10K4R33 R36 R40 R54 10K 1W72-RM10K-1WATT1R31 15K 1/4W72-RM15K1R59 27K 1/4W72-RM27K2R13 R67 47K 1/4W72-RM47K1R19 68K 1/4W72-RM68K2R5R39 82K 1/4W72-RM82K1R35 100K 1/4W72-RM100K3R11 R41 R42 100K 1W72-RM100K-1WATT3R8R15 R16 180K 1/4W72-RM180K1R34 220K 1/4W72-RM220K5R20 R21 R43 R52 R53 220K 1W72-RM220K-1WATT2R1R29 330K 1/4W72-RM330K1R58 470K 1/4W72-RM470K2R6R12 820K 1/4W72-RM820K1R28 1M0 1/4W72-RM1M6R3R4R9R17 R18 R44 100R 4W72-RWW100R-4W2R25 R26 120R 6W72-RWW120R-6W1R24 1K0 6W72-RWW1K-6W1R32 3K3 4W72-RWW3K3-4W1R30 SEMICONDUCTORS 1N400272-D-IN40024D6D7D8D9 1N400772-D-IN40074D1D2D3D4 GP02-40 (4KV)72-D-GP02-402D5D10 9V1 ZENER72-D-BZX55C9V12Z1Z2 15V ZENER72-D-BZX55C15V1Z3 2N390472-T2N39043TR9 TR10 TR11 2 2N390672-T2N39062TR1 TR2 J17572-FET-J-1751TR6 BD64772-TBD6471TR7 RC455872-IC-RC4558P2IC1IC2 CAPACITORS 47p 500V ceramic72-C47P-500VCD1C29 100p 1KV ceramic72-C100P-1KVCD1C10 220p 1KV ceramic72-C220P-1KVCD2C7C12 470p 1KV ceramic72-C470P-1KVCD1C6 1n0 1KV ceramic72-C1000P-1KVCD1C9 4n7 1KV ceramic72-C4700P-1KVCD4C30 C31 C32 C33 33p100V axial72-C33P-100VCA2C41 C42 100p100V axial72-C100P-100VCA1C43 560p100V axial72-C560P-100VCA1C4 2n2100V axial72-C2N2-100VCA1C3 6n8100V axial72-C6N8-100VCA1C46 22n100V axial72-C22N-100VCA2C15 C47 100n100V axial72-C100N-100VCA9C2C18 C21 C27 C28 C36 C50 C60 C61 330n 50V axial72-C330N-50VCA1C39 22n 400V poly box72-C22N-400VP3C5C16 C17 47n 400V poly box72-C47N-400VP1C14 100n 250V poly box72-C100N-250VP1C13 1u5 35V tant72-C1.5-35VT1C1 2u2 35V tant72-C2.2-35VT1C8 22u 450V elect rad72-C22-450VER2C25 C26 47u 63V elect rad72-C47-63VER2C11 C64 100u 16V elect rad72-C100-16VER4C51 C52 C53 C62 100u 400V elect rad72-CAP-100400V2C22 C23 220u 35V elect rad72-C220-35VER2C19 C40 4700u 35V elect rad72-CAP-470035V1C48 CONNECTORS 3way 0.1”72-HEAD-3W-23HTR0 HTR1 HTR2 CRIMP CONNECTORS72-CRIMP-PCB-TAB16TX1 - 14LS1 (x2) SOCKETS 1/4” MONO JACK SKT72-SKT-JCKBNBG4SK1 SK2 SK3 SK4 SWITCHES 3 Large slide DPDT horiz73-SWT-SLIDER-DP1SW1 Mini Toggle SPDT vert73-SWT-M-TGL-PCB1SW2 POTENTIOMETERS 1M073-POT-A1M1RV1 250K LIN DUAL GANG73-POT-B250K-DG1RV2 50K73-POT-50KB1RV3 VALVE BASES B9A PCB valve base73-VAL-SOCKET4V1V2V3V4 FUSE HOLDERS72-FUS-HLD-PCB-24FS1 FS2 FS3 FS4 TEST PIN73-PIN-TERM1TP0 TO220 HEAT SINK71-HS-PF7521TR7 FLYING LEADS ETC Cathode heater leadC00-LEAD-VEL12- HTR 1insert into HTR0, HTR1 & HTR2 Reverb input leadC00-FLY-TRAMP-R1REVERB IN Reverb output leadC00-FLY-V12R1REVERB OUT Grommet45-GROMM-21put over reverb leads before soldering into PCB 1 VELOCETTE 12R CIRCUIT DISCRIPTION Please refer to circuit diagram for DC voltages and other information INPUT SECTION AND PREAMP SK1 and SK3 are the LO and HI sensitivity inputs respectively. When the LO socket is used R5, R39 and R3 act as a potential divider to reduce the input level to the preamp. C3 has two purposes, firstly to block any DC from the input that may unintentionally be present, this would otherwise change the bias point of the first valve stage, secondly the value of the capacitor has been chosen so that there is a slight roll off of lower frequencies, this prevents the sound from getting too muddy. V1a is the first gain stage and is configured as a cathode bias, common cathode, voltage amplifier with bypassed cathode resistor for increased gain. R6 and C6 give a slight presence lift and the frequency of the Bright effect is set by C7, which, when switched in, is across pins 2 and 3 of RV1 (Volume). Obviously connected like this the amount of brightness added will decrease as RV1 is turned up. V1b is the second gain stage configured similar to before, C9 is added across the anode resistor R8 to smooth out the top end. The Tone network is passive and controlled by RV2. This is a dual ganged potentiometer, one part of which effectively controls the mids (RV2B) while the other part inversely controls the treble (RV2A). R28, R34 and R35 act as a potential divider to lower the signal sent to the reverb circuitry. REVERB SECTION The signal from the preamp is fed into IC1A which is configured as a boot strapped voltage follower. Z1 and Z2 have been added to prevent any nasty spikes from damaging the opamp, this should in practise never happen. C4 and R44 roll off a lot of the lower frequencies before the signal gets sent to IC1B and IC2A. These opamps are configured for current gain, the actual gain being dependant on the impedance/frequency curve of the reverb tray. Because of this it is crucial to the correct operation of the reverb that the right reverb tray is used. This should be an Accutronics 8CA3B1B. The output of the reverb tray goes into IC2B. This is configured as a differential amplifier as a way of reducing any hum that may be picked up on the sensitive reverb return leads. RV3 controls the level of the reverb. Across pins 1 and 2 is TR6, a J175 FET. When SK4 is shorted out, by a footswitch, TR6 is also effectively shorted which results in the reverb being turned off. 2 The reverb signal is then mixed with the dry signal, via R58, before going into the phase splitter. POWER STAGE The phase splitter (V2A and V2B) is a differential input splitter which produces the two anti phase signals necessary to drive the push pull output stage. V3 and V4 are the two EL84 output valves connected as a push pull, cathode biased class A power amplifier. The quiescent current is set by R24, which is bypassed by C19 for extra gain. SW1A and SW1B is an electrically robust slider switch used to switch the power valves from Pentode to Triode operation. For Pentode operation the screen grid (grid 2, pin 9) is connected, via the screen grid current limiting resistors R25 and R26, to the highly smoothed screen grid supply, G2 - positive pin of C23. For Triode operation the screen grid of each valve is connected to the corresponding anode. Triode operation basically reduces the power output to a bit less than half and also reduces the high frequencies in the overall sound. D5 and D10 have been added to give protection to the output transformer should a fault arise. OUTPUT TRANSFORMER AND SPEAKER CONNECTIONS The output transformer has secondary taps for 16, 8 and 5.3 . The 16 tap is used to drive the External Speaker Output, SK2. When a jack plug is inserted into SK2 the internal speaker is disconnected. The three LINK positions are provided on the PCB so that different impedance internal speakers can be used in production. Depending on whether the internal speaker is 16, 8 or 5.3 the correct LINK should be fitted. This has been done purely so that different impedance speakers can be used if there are any problems with supply. POWER SUPPLIES All three supplies, HT, ac heater, and DC supplies have secondary fusing on the PCB. This is to protect the mains transformer and for approvals. The HT supply is a very simple bridge rectifier diode network, with 4n7 1KV capacitors across each diode for EMC reasons, which is then smoothed by C22, to supply the centre tap of the output transformer. This is then further smoothed by R32/C23, R30/C25 and R31/C26 to supply the screen grids, phase splitter and preamp respectively. R29 is added to discharge the high voltage capacitors when then unit is turned off. The ac heater supply is simply connected via a twisted pair connecting lead to V3 and V4 after first going through the secondary fuses 3 The 25.2V DC supply is highly regulated supply using a BD647 (TR7) as the main regulating device. (Please ensure that the small clip on heat sink is attached to TR7) TR1 and TR2 provide a constant current source for Z3 the 15 volt zener. The output voltage is set by the ratio of R59 and R67 which provide the feedback to TR7 via TR9 and TR10 to stabilise the whole circuit, and TR11 with R80 and R81 form a current limiter. This allows the supply voltage to ramp up at switch on when the heater filaments of the preamp valves draw considerably more current while cold. R27 and R57 halve the supply voltage to provide the opamp bias voltage, and as shown on the circuit diagram the DC supply is routed first through the two filaments in V2 in series and then through the two filaments in V1. This will result in each filament having the nominal 6.3 volts across them. Paul Stevens 2 January 1997