Service manual

Master 128

This unit is sent out from the original manufacturer with the 64K Sideways RAM paged in and therefore the

two 32K ROM sockets (IC37 & IC41) paged out.

Confusion often sets in when ROMS or EPROMS are plugged into the M128 here and it does not appear to

any further. To alter this ROM/RAM situation, carry out the following:

LK18 fitted in EAST position allows 32k ROM in IC41

LK19 fitted in EAST position allows 32K ROM in IC37

As an aide-memoire, if the link is set toward the ROM on the circuit board then the ROM is enabled. If it is

set towards the RAM, then the RAM is enabled.

Master Compact

A substantial quantity of Compacts that are recieved by our Central Workshop are found to have no fault.

All that is required is the unit to be configured correctly via an R-power on.

As this is not documented clearly in the-Welcome Guide this problem is likely to continue for some time.

Unlike the Master 128, when the R-Power-On reset is performed on the Compact, the default values of the

status are set to a sensible value.

If units are returned requiring only re-configuration then the unit will be treated as no fault found, and a

charge will be levied.

Archimedes

Like the Master 128 and the Master Compact, the Archimedes also has some configuration values that are set

in non-volatile memory. Similarly, these values can be set to pre-defined values using R-power on. However,

there are two different default values present in the 300 series Archimedes machines, and R-power on will

toggle between these values. If you try to re-configure using R-power on and your screen turns purple and

rolls violently, then don't worry, as this is one of the defined configurations. (It is used for a different type of

monitor). Repeating the R-power on should return you to a stable picture.

We have experienced some problems with early machines which have manifested themselves as 'Disc Error

10'. Some of these problems are due to drive buttons fouling the front plastic moulding when a disc is

inserted. These can frequently be fixed by removing the front panel (two screws inside the machine), being

careful to remove the speaker/LED connection cable from the main circuit board, slackening off the four

screws securing the disc drive to its bracket, tipping the drive so it points upwards as far as possible with

these four screws in place, and tightening the screws to hold the drive in this position. The front panel can

then be replaced, and the machine tested.

Doc. 999,0031 December 1987 -8- Acorn Engineering News