Acorn BBC Master 128, Руководство по обслуживанию

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Master Series Service Manual
3 Disassembly and assembly
To service the BBC Master Series Microcomputer, first disconnect the
power supply plug from the mains and remove all peripheral connections
from the computer.
To disassemble
The lid of the microcomputer case may be removed after undoing the
four fixing screws underneath the case. DO NOT remove the lid with the
mains power connected.
Inside the microcomputer are four main sub-assemblies:
keyboard
speaker and battery unit (the cartridge nest)
power supply unit
main printed circuit board
To remove the keyboard, first unplug the 2 keyboard connectors from
the main printed circuit board. Undo the 3 screws holding the keyboard
to the case bottom, and the 1 screw which holds it to the power supply
unit.
To remove the speaker and battery unit, simply lift the casing upwards
and then unplug the two connectors joining it to the board.
The power supply unit is connected to the main circuit board by seven
push-on connectors which must be unplugged. Three screws on the
underside of the case are undone allowing the unit to be removed. On
reassembly, ensure that the same type of screw is used (M3x6mm).
The main printed circuit board is removed complete with the metal
back-plate. To remove the main printed circuit board, undo the 4
fixing screws which pass through the cartridge connectors into the
case bottom, and the 1 screw which holds the metal back-plate to the
power supply unit. Remove the circuit board from the case by lifting
it slightly at the rear and then sliding it backwards.
To reassemble
Replace the main printed circuit board by putting the front edge (with
connector headers) in first and pulling it forwards until the metal
back-plate drops in. Make sure that all the lugs on the lower case
locate with all the correct points on the PCB and back-plate. Replace
the 4 PCB fixing screws which pass through the cartridge connectors,
and the single screw which joins the back-plate to the power supply
unit.
Reconnect the power supply, being careful to route the wires neatly,
and connect the wires (seven) to the push-on connectors on the PCB,
being very careful to get the polarity right.
PCB connectors 5V must have a red wire attached (three)
PCB connectors marked OV must have a black wire attached (three).
The connector marked -5V has the purple wire attached (one).
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