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Fender Twin Amp 1994, Service Manual

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Page: 10 / 23

Fender Twin Amp 1994 Service Manual Download Page 10

’94 TWIN AMP

SERVICE MANUAL

ADDENDUM

This addendum contains important modification and revision information including parts and revision “C” schematics.
Please attach to the existing service manual for the ’94 Twin Amp.

CONTENTS:

Notices

Description of changes
Parts list
Schematics/diagrams

Fender Musical Instruments Corp.

7975 North Hayden Road Scottsdale, AZ 85258

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Summary of Contents for Twin Amp 1994

Page 1: ...809 000 120V SERVICE MANUAL CONTENTS Notices Specifications Parts lists PCB assembly Chassis assembly Cabinet assembly End item Schematics diagrams Fender Musical Instruments Corp 7975 North Hayden Road Scottsdale AZ 85258 ...

Page 2: ...arts marked with an asterisk indicate the required use of that specific part This is necessary for RELIABILITY and SAFETY requirements DO NOT USE A SUBSTITUTE A coded naming convention is used in the description of certain parts The codes and what they mean are as follows CAPACITOR CODES HARDWARE CODES CAP AE Aluminum Electrolytic BLX Black Oxide CAP CA Ceramic Axial CR Chrome Plated CAP CD Cerami...

Page 3: ...jacks Reverb Post effects loop Preamp Out Post reverb 1 3 dbv nominal level Recommended load 22 k Ω minimum Power amp in 1 3 dbv sensitivity 1130kΩ input impedance Balanced Line Output Derived from the output transformer fully balanced 3 dbv nominal level into 600Ω or greater Pin 1 floating pin 2 pin 3 Amplifier Load Impedance Switch selectable for 4 8 or 16 Ω Power Output OUTPUT HIGH setting 100 ...

Page 4: ...in than previously found in a Fender tube amp The signal from pin 9 of Relay K1B feeds through the Channel Two Gain control R25 to the first V3A and then second V3B stage of the overdrive circuitry From V3B the signal is fed to through the Treble R35 Bass R36 and Mid R37 tone controls Finally the signal travels through the channel two Volume control R39 which also contains the Channel Select switc...

Page 5: ...y switch in the On position With a digital voltmeter set to its most sensitive DC voltage scale connect the test probes to the test points J11 J12 labeled Bias Adjust the Output Bias Adjust control R94 to read 08 VDC 80mVDC This will Bias V9 V10 Now connect the test probes across the Balance test points J10 J11 The meter is now referenced to the 80mVDC instead of ground Adjust the Output Balance A...

Page 6: ...NLY PRINTED CIRCUIT BOARD ASSEMBLY QTY PART DESCRIPTION REFERENCE DESIGNATION 1 048973 CABLE RIBBON 9 CKT 15 IN P3A 1 048972 CABLE RIBBON 9 CKT 9 IN P2A 1 038691 CAP AE AX 4 7 UF 50V C35 7 009512 CAP AE AX 22 UF 25V 20 C1 5 11 24 28 53 61 4 024819 CAP AE AX 22UF 500V C22 42 43 44 4 036954 CAP AE RDL 22UF 63V 20 C36 37 59 62 4 024820 CAP AE AX 47UF 350V C40 41 51 52 1 028471 CAP AE RDL 47UF 50V 20 ...

Page 7: ...0 61 67 140 6 025117 RES CF W 5 220K R99 102 110 111 2 033095 RES MOX FP 1W 5 1Ω R89 90 1 037354 RES FILM 1W 5 4 7K R80 1 041739 RES MOX FP 1W 5 6 8K R104 1 027349 RES FILM 1W 5 10K R42 1 041738 RES CF 1W 5 15K R43 1 027350 RES FILM 1W 5 22K R79 1 027352 RES FILM 1W 5 91K R73 1 027353 RES FILM 1W 5 100K R72 1 041277 RES CF 2W 5 820Ω R112 1 041740 RES MOX FP 2W 5 4 7K R103 1 041737 RES CF 2W 5 33K ...

Page 8: ...T T3 100V 115V 230V 240V 1 026478 XFMR OUTPUT 100W 4 8 16 Ω T2 1 037099 XFMR REVERB VIBROVERB T1 FOOTSWITCH ASSEMBLY QTY PART DESCRIPTION REFERENCE DESIGNATION 1 028895 CABLE ASSY FTSW RT ANG 12 FOOTSWITCH CABLE 2 006260 DIODE 1N4448 1N914B SIGNAL CR1 3 2 031017 DIODE ZEN 1N5223B 2 7 V 5 CR2 4 1 047800 FTSW ASSY 3BTN GAIN CH REV COMPLETE FOOTSWITCH 1 037036 JACK PHONE PCB MONO CA PREMIUM J1 3 0318...

Page 9: ... 94 TWIN AMP BLOCK DIAGRAM ...

Page 10: ...ion and revision information including parts and revision C schematics Please attach to the existing service manual for the 94 Twin Amp CONTENTS Notices Description of changes Parts list Schematics diagrams Fender Musical Instruments Corp 7975 North Hayden Road Scottsdale AZ 85258 ...

Page 11: ...pair Parts marked with an asterisk indicate the required use of that specific part This is necessary for RELIABILITY and SAFETY requirements DO NOT USE A SUBSTITUTE A coded naming convention is used in the description of certain parts The codes and what they mean are as follows CAPACITOR CODES HARDWARE CODES CAP AE Aluminum Electrolytic BLX Black Oxide CAP CA Ceramic Axial CR Chrome Plated CAP CD ...

Page 12: ...ttempt the above modification to earlier revision PCBs Added RF emissions suppression capacitor C64 P N 025995 across the high voltage transformer secondary prior to the full wave bridge rectifier circuit Performance modifications Added CR32 and changed R124 and R134 to ensure that Relays K1 K2 and K3 drop out when de energized See zone 7B on Rev C schematic Refer to Tech Note TN95 4 Upgraded the ...

Page 13: ...ODE 1N4006 800V CR2 3 5 11 14 15 34 37 14 006260 DIODE 1N4448 SIGNAL CR16 17 19 20 22 30 32 2 041811 DIODE ZEN 1N5368B 47V 5W 5 CR33 38 3 047234 RES CF 1 6W 5 1 8k R59 117 155 4 024962 RES CF 1 4W 5 560Ω R41 52 124 137 1 026549 RES CF 1 2W 5 1 5k R134 3 025117 RES CF 1 2W 5 220k R99 100 101 1 047768 SCHEM REDU W SERV 94 TWIN AMP REVISION C 1 049976 SWITCH TOGGLE DPST DC W NUT S9 REFER TO TECH NOTE...

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Page 16: ... cause burning pitting and eventual welding together of the switch contacts Therefore when the amplifier is switched to the LOW power mode the high voltages at the output tubes remain high but the Bias voltage drops The result is a severely under Biased output stage that quickly overheats REQUIRED ACTION A new style switch has been specified for this application Determine if the old style switch i...

Page 17: ...e pair of White switch leads to the two points labeled BLU Solder the pair of Black switch leads to the two points labeled BN Revision E PCB s are silk screened TO OUTPUT SWITCH WHT BLK White leads to WHT Black leads to BLK Re install the PCB Verify proper switching of the B and negative Bias voltages WARRANTY CLAIM INSTRUCTIONS The above modification should be performed on any 94 Twin Amp requiri...

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