Fender blues junior service manual
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Page 1
BLUES JUNIOR SERVICE MANUAL NOVEMBER 1995 IMPORTANT NOTICE: The information contained herein is CONFIDENTIAL and PROPRIETARY to Fender Musical Instruments Corp. It is disclosed solely for use by qualified technicians for purposes of equipment maintenance and service. It is not to be disclosed to others without the expressed permission of Fender Musical Instruments Co. All specifications subject to change without notice. For warranty repair service, only Fender specified part numbers are to be used. It is recommended they also be used for post-warranty maintenance and repair. Parts marked with an asterick ( *) 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 = Ceramic Disk HWH = Hex Washer Head CAP MPF = Metalized Polyester Film M = Machine Screw CAP MY = Mylar NI = Nickel Plated CAP PFF = Polyester Film/Foil OHP = Oval Head Phillips PB = Particle Board RESISTOR CODES PHP = Pan Head Phillips PHPS = Pan Head Phillips Sems RES CC = Carbon Comp SMA = Sheet Metal "A" Point RES CF = Carbon Film SMB = Sheet Metal "B" Point RES FP = Flame Proof SS = Stainless Steel RES MF = Metal Film TF = Thread Forming RES WW = Wire Wound ZI = Zinc Plated
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BLUES JUNIOR SPECIFICATIONS Type PR 295 Input impedance: 1M ohm Power output: 15 Watts R.M.S. @ 5% T.H.D Rated load impedance: 8 Ohms Speaker compliment One 8 ohm 12" Eminence, replica of Jenson P-10 Dimensions: Height: 16 inches (41 cm) Width: 18 inches (46 cm) Depth: 9-13/16 inches (25 cm) Weight: 31 lbs. (14 kg) THEORY OF OPERATION J1 is a high-sensitivity input with an input impedance of about 1M Ω. V1B is the first gain stage which also contains the "FAT" switch. The FAT feature is activated by grounding the node between bypass capacitor C3 and R9. Via the FAT switch (S1) or the optional footswitch, the junction of R52 and R54 can be grounded. With zero volts applied to the gate of Q1, the JFET will essentially ground C3, activating the FAT feature. The output of V1B couples to the VOLUME control (R7). The VOLUME control is actually a preamp overdrive control that adjusts the level of distortion. C2 attenuates high frequencies and C1 attenuates low frequencies at high distortion settings. This takes the edge off the distortion and prevents the speaker from flapping. V1A provides a gain of about 40, and drives the tone control circuitry. After the tone controls, the signal is fed to V2B, which drives the MASTER volume control (R41). From the MASTER volume, the signal splits to feed the power amplifier and the Reverb. U1A makes up a typical solid-state reverb drive circuit. U1B is the reverb recovery or sense circuit, which drives the REVERB control (R51). The reverb signal is summed with the dry signal at C6, which couples to the input of the Phase Inverter (V3). The output tubes (6BQ5/EL84) are arranged in a push-pull configuration that will produce fifteen (15 ) watts R.M.S. into eight (8) ohms @ 5% THD, 1kHz. The output bias is derived from the -15Vdc supply. The voltage divider at R31 & R37 determines the bias voltage (-10.7 Vdc). C14 filters the ripple to 1mV or less.