ARCAM Arcam-T51-Service-Manual free download

File name Arcam-T51-Service-Manual.pdf

Service Manual T51 Issue 1.0 DiVA T51 AM/FM Tuner ARCAM Contents List ! Contents list ! Circuit description ! Circuit diagrams ! Component overlays ! Circuit board parts list ! General assembly parts list T51 Tuner Circuit Description Stereo Decoder Power Supply Stereo decoding is performed by LA3401 (Z8). The 38kHz reference signal is accurately created by ceramic resonator Mains voltage selection is made by placing a fuse, of X3 and does not require adjustment. appropriate value, in the 115V or 230V position. Stereo separation is adjusted for maximum by preset RV1. The single secondary is rectified and regulated and This IC also contains FM/AM audio switching and muting supplies four regulators. functions. Z7 is always powered when the mains is connected and keeps the preset memory of the micro controller intact. Audio Filters & Output The high-value capacitor (C84) will keep this data safe, for a limited time, in case of mains power failure. The left and right channel audio outputs from Z8 are filtered by the de-emphasis network of R1, C1 etc. The Z5 provides the main 12V supply rail for the RF and audio correct de-emphasis network is selected by the position of circuits. This is always connected, except for the supply to jumpers JP3 & JP4 on the pins of SK8. C2 & C102 the FM front end, which is disabled by Q2 when the unit is (220pF) are selected for 50us and C3 & C103 (560pF) for turned 'off'. 75us de-emphasis. Z4 powers the LED back light on the display PCB. The final filter, based on Z3, is a two-pole low-pass circuit with a cut-off frequency of around 20kHz. Also included Z6 is the 5V digital supply for the micro controller. is a 19kHz notch filter, L1 & C4, that removes most of the residual pilot tone. FM Tuner & IF Muting The FM aerial input is mixed in the front end FE1 which provides a 10.7MHz IF output. This is filtered and When the power switch is turned off Q5 is switched off, amplified by ceramic filters CF1 & CF2 and the circuit enabling the mute circuitry of the stereo decoder (Z8) via based around Q9 & Q10. A third filter CF3 can be put in diode D9. This removes the need for output muting circuit by fitting jum