G-DEC_Jr._Service_Manual 电路图.pdf
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1、G-DEC Jr (This is the model name for warranty claims) Fender Musical Instruments Corporation, 8860 East Chaparral Road Suite 100 Scottsdale, AZ 85250 Issued: February, 2007 p/n 2351000000 (120V) SERVICE MANUAL ATTENTION: WARRANTY SERVICE PROCEDURES Domestic (U.S. LOOP Start/Stop switch; and headphon
2、e present status are read via the analog multiplexer U6-A. The output of the multiplexer is read serially by the right channel of the CODEC and sent to the uDSP system Note: Troubleshooting the uDSP system to com- ponent level beyond verification of power supplies, clock, and data signals is NOT rec
3、om- mended. G-DEC Jr (This is the model name for warranty claims) 7 MIDI System MIDI Input signals from the external MIDI INPUT Jack (J4) are optically isolated via U22 and sent to the Rx line of the uDSP UART controller within U10 for processing. When MIDI is selected on the LOOP Selector, the MIDI
4、 signal being received is passed through to the Tx line of the uDSP UART and to the MIDI IN of the SAM2195 Dream Synthesizer chip U20. The SAMP2195 then plays MIDI sounds based on the commands being sent from the external MIDI sequence source. With internal LOOPS selected the external MIDI in- put i
5、s ignored and MIDI IN signals are generated by the uDSP system under control of the LOOP SE- LECT and KEY SELECT controls. The rate is controlled by the TEMPO control. Audio output from the SAM2195 Dream Synthesizer chip is mixed in at summing op-amp U2-B via R50/R54. The audio output of U2-B is mix
6、ed in with the instrument post processed (effects and amp types added) and Auxiliary Input audio at U2-A. POWER SUPPLIES The power transformer secondary windings are con- nected to the main PCB at P5 through P10. The +/-20VDC power supplies for the solid-state power amplifier are derived from the re
7、d-yellow-red secondary of the power transformer via full bridge rectifiers D4/D5 and D2/D3, and main filter caps C14 and C8. The yellow center tap lead and the systems chassis connection are placed between these caps, making this the system ground star. The +/-12VDC power supplies for the op-amps ar
8、e regulated down from the +/-20 VDC supplies through dropping resistors R13-14 and Zener Diodes D6 and D7. The +11.5VDC power supplies for the Digital circuitry is derived from the brown-brown secondary of the power transformer via full bridge rectifiers D15, D16, D17 and D21 and filter caps C34. Th
9、is raw supply is then regulated down to +5VDC by U5 (7805). The +5VDC supply powers multiplexer U6, Front Panel LED drivers Q5-Q7 and the D.C. reference voltage string R41-R43 for the high-low reference level for front panel potentiometers. The +5V is regu- lated down to 3.3v and 1.25V via U18 and U
10、17 respectively. The 3.3V and 1.25 V supply power to the uDSP system components and the MIDI I/F components including the SAM2195 Dream Chip U20 and U22 MIDI input opto-isolator. Reset control- ler U12 monitors the +5V supply and shuts down all ICs in the event of power loss. USER INTERFACE The 4 -
11、16 position encoders (S2 S5) for the LOOP, AMP, KEY and EFFECT SELECT are read via the port expander U9 and the data sent to the uDSP sys- tem via the I2C interface lines SCL and SDA. The 4 potentiometers VOLUME(R51), GAIN(R49), TONE(R44), and TEMPO(R31) generate DC volt- ages (+1.0V to +4.0V) that
12、are read by the analog multiplexer U6. IO0-IO3 are the digital control lines used to multiplex these analog signals which are sent serially to the system CODEC U13 on the Rin channel. The LOOP START/STOP button and the state of the HEADPHONE present signal are read in a similar manner. The uDSP syst
13、em reads the state of these controls and inputs digitally from the CO- DEC. The LOOP VOLUME is a conventional analog con- trol which accepts the MIDI left and right loop audio signals from the SAM2195 MIDI Synthesizer via the mixer op-amp U7-B. G-DEC Jr (This is the model name for warranty claims) *
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