Acorn Computers Limited Winchester disk 110, Руководство по обслуживанию

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7 Fault finding
When the Winchester Disc unit is powered-up, the hard disc will spin up to
speed in about 10 seconds. This process produces a rising pitch humming noise
which means that the hard disc is spinning. Note that there is also a noise
from the cooling fan, but this noise is lower in pitch and does not take time
to build up. If the disc is not spinning then disassemble the unit and check
the power supply and connections.
Make sure that the ADFS ROM is plugged into one of the test BBC
Microcomputer's sideways ROM sockets. If the machine will not access the
Winchester then type
*ADFS
If the unit powers up correctly but still won't work then print out the
contents of the status register as follows:
PRINT ~?&FC41
The result should be zero. If the result is FF then the ribbon cable is
disconnected.
7.1 Power supply
The three major components of the Winchester Disc unit - the disc drive, the
disc controller board, and the Host Adapter board - are each powered from the
switch-mode power supply unit which sits at the back left of the case. The
power supply output cables are colour coded as follows:
black ground
red +5V
12V
The power supply can be tested by measuring the +5 voltage between the black
and red cables, and the +12 voltage between the black and yellow cables. The
allowable voltage ranges are as follows:
+5V (black and red) 4.9V to 5.2V
+12V (black and yellow) 11.4V to 12.6V
These measurements should be made with all connectors in place.
Next measure the current drawn by each of the three components specified above
from the +5V and +12V supplies. Two of the components are each supplied via a
four-way plug-in connector, and the current measurement should be made in
series with either the red cable (+5V) or the yellow cable (+12V). The
connections to the meter to do this must be made with the power switch off.
The measurements must be made after power-up as some of the circuitry, when
working correctly, will alter its current consumption with time as shown
below. The current drawn by each component from each voltage rail should be as
follows:
Winchester hard disc unit, see figure 2:
+5V around 1 to 1.5A
+12V up to 4.5A on power-on falling to around 2A when up to speed
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