ARCAM Arcam-7R-8R-8P-int-sm free download

File name Arcam-7R-8R-8P-int-sm.pdf

ALPHA ONE/7R/8R/8P AMPLIFIER SERVICE MANUAL Arcam Alpha One/ 7R/ 8R/ 8P Amplifier Service Manual Issue 1 Serial Number 001 - (Paul Newton/ Haider Bahrani Sept `98) Circuit Description source for the differential input stage. The Alpha One / 7R/8R and 8P share a common The output devices are 'n' channel mosfets SMF045. pcb. The circuits are very similar and the main Zener diodes D103,104 limit the voltage swing within differences are the remote volume facility and extra safe limits for the output devices & fusible resistors power output on the 7R and 8R and a switch to R105, 106 provide overcurrent damage to the bypass the phono stage to enable its use as an extra devices. line level input and the AV processor switch on the Alpha 8R integrated amplifier. The 8P power A proportion of the output current appears across the amplifier utilises the same power amplifier circuit as protection network R41,42. If this becomes too high the Alpha 8R integrated amplifier. Q17 is turned on and mutes the output. High D.C. levels at the output will also mute the output. There Power Supplies are no output fuses on the Alpha One, 7R and 8R/8P amplifiers. The muting is done by the mute ic The ac output of the toroidal mains transformer is Z303 and its associated compontents. The mute rectified and smoothed by D201-204 and C204, 205. operates on switch on/off and if an over current or This is then regulated to +/-15V by Z201, 202 to over voltage condition occurs. The power led glows power the phono and tone control stages and the amber when the mute circuit is operative and glows d.c. servo. green in normal use. The Alpha 7R and 8R transformers have an extra Removing the Alpha One/ 7R/ 8R/ 8P Transformer tapping which is used for the remote volume circuit. The ac in is regulated to 5V by zener D902 and The toroidal transformer is extremely well secured to associated components and this is then used to the main pcb with a double sided adhesive gasket. power the microcontroller Z901 and remote receiver. To remove the transformer you must break this adhesive bond by cutting through the gasket. This Phono Stage (Not applicable to Alpha One) will be easier if the transformer is warm. Use a cheese wire under the transformer, pulling The phono stage consists of a dual opamp Z305, one backwards and forward