ARCAM Arcam-A32-int-sm free download

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Service Manual A32 Issue 1.0 FMJ A32, P35 & P35/3 Amplifiers ARCAM Contents List ! Phono board L870 o Circuit description o Component overlay o Parts list o Circuit diagrams ! Amplifier & PSU board L882 o Circuit description o Component overlay o Parts list o Circuit diagrams ! Display board L928 o Component overlay o Parts list o Circuit diagrams ! Preamplifier board L937 o Circuit description o Component overlay o Parts list o Circuit diagrams ! 3rd Channel Amplifier board L911 o Component overlay o Parts list o Circuit diagrams ! Transformer specifications o L914TX o L915TX ! General assembly o A32 - Mechanical parts list o P35 - Mechanical parts list o P35/3 - Mechanical parts list Phono Board L870 Contents ! Circuit description ! Component overlay ! Parts list ! Circuit diagrams AV8 Phono Board Circuit Description Refer to circuit diagram L870 sheet 1 The phono board is a simple single stage RIAA amplifier and consists of two channels of high gain amplification, and the ability to switch between moving magnet (MM) and moving coil (MC) settings. PSU The unit derives its + 15V regulated rails from the unit it is fitted into with only local decoupling capacitors on board. Interface The unit connects to the host unit via a 8 way connector. Amplification The left channel has designators beginning with 100, and the right with 200. For the purposes of this description the left channel will be described, as the right channel is the same in all respects. The amplifier is a small signal class A voltage feedback amplifier with switch able gain. The input consists of an actively loaded differential pair of very low noise PNP transistors (TR106, TR107). These transistors are very specific and should only be replaced with identical parts with the E grade high gain. TR100 and TR101 form a current source for the pair, which sets the quiescent current for the entire amplifier. The active load consists of TR110 and TR111, which forms part of the differential current mirror with TR112, TR113 & TR114. This differential stage also has an active load (TR102 & TR103) to keep gain to a maximum. Both of these differential stages are designed to have as much gain as possible to enable the single stage design. The RIAA response is achieved in the feedback network: C101, C110, C111, C112, C119, C120 and R115, R112. C115 is used to correct between MM and MC gains as the amplifier is non-inverting. SW100 switches between MM and MC. Two poles of the switch change between the different loading required for each type of the cartridge: R108 & C109 for MM and added in parallel for MC R104 & C108. The other two poles change th