Solid State Logic AWS 900+ Owner's Manual page 132

Troubleshooting
To give an example of an audio fault, examine the following problem. By working through this example you will
see the basic principles of fault finding at work. You have Channel 24 routed to Track Busses 1 and 2 pre-fader.
When monitoring the Track Busses you notice that the audio can only be heard on the left monitor output.
Your first step is to refer to the AWS 900+ Centre Section block schematic. From this you will see that the
channel's output passes through five different modules before reaching the monitors. We can halve the problem
by checking the signal path halfway through the chain. The monitor meters are fed from the output of the
629951 module. Do the meters show the same level on left and right? If the meters show the same level then
the problem is post the 629951 card on either the 629952, 629953 or 629954 card. If the meters show different
levels, then the problem is either on the channel's output, the 629919X1 card or the 629951 card.
For the sake of this example we will assume that the level shown on the meters was different. Using the same
principle we will try to eliminate modules from the signal path. Again referring to the AWS block schematics you
can see that the Track Bus metering is taken post the 629919X1 card's output, but pre the 629951 module's
input. Do the Track Bus meters show the same signal level? If they do, then the problem is on the 629951 card;
if not then the problem lies with the channel strip or the 629919 module.
Again for the sake of the example, we will assume that the level on the Track Bus meters was different. Halving
the signal path again, de-assign Channel 24 from the Track Busses, route the same signal to Channel 23 and
assign it to Track Busses 1 and 2. Can signal be heard on the right monitor? If it can then you have identified in
a matter of minutes that Channel 24 has a faulty Track Bus output stage. If audio cannot be heard, then you
have identified that the 629919X1 Track Bus card is faulty.
The next step in either case would be to follow the module removal instructions below and re-seat the module
in its slot to ensure that a valid connection is made. Once re-seated, test the signal path again. If there is no
change, a replacement will be required.
Control Faults
Control faults will typically result in either the corruption of display information, or the failure of encoders and
switches. The majority of the console's display and control functions are performed by the 629645X1 CPU,
which is located behind Bay 3's Meter Panel. The CPU uses two methods of control. These are Multidrop Bus
and Live Bus. Both busses are bidirectional and carry control data, such as switch presses, to the CPU as well
as display data, such as LED illumination commands, to the displays.
Multidrop Bus data is used to control all of the console's audio processing modules, these are the 629921X1
Channel Strips, 629651X1 6-Track Select, 629652X1 2-Track Select, 626653X1 Gain and MDAC Control,
620654X1 Monitor Outputs, 629918X1/2 Dynamics, 629918X1/2 8-Track and Aux Bus, and the 629928X1
Compressor. All other panels are controlled by the Live Bus. Referring to the AWS 900+ Control Block
Schematic you will see that four Multidrop busses, one per bay are used. The Multidrop data from the CPU is
connected to each of the channel backplanes and the centre buscard using a 20-pin IDC ribbon connector. The
audio processing card then sit on this bus, sending or receiving data as required.
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AWS 900+ Owner's Manual