Control Faults - Solid State Logic AWS DELTA 916 Owner's Manual

Troubleshooting
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.
C F
ONTROL AULTS
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 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.
The following problem highlights a Multidrop Bus fault and explains how the fault might be located. After powering on the
console you notice that all of Bay 2's channel strip LEDs are extinguished, and the switches do not respond; all other bays
are working correctly.
Once again refer to the AWS Control Block Schematic. From the diagram you can see that Multidrop Bus data for Bay 2
is connected to socket PL2 on the 629645X1 CPU. Power down the console and remove the channel meter from Bay 3
(refer to Replacing Modules on the following page). Located behind the channel meter is the CPU. Remove the metal
screen which surrounds the CPU and locate connector PL2. Remove and then reinsert the connector to ensure that a
sound connection is made. Re-assemble the console and check the condition of the fault.
For the sake of the example we will assume that this did not resolve the problem. The next step would then be to inspect
the other end of the Multidrop Bus connection. The diagram shows that the data ribbon connects to the CPUA socket
on the 629640X1 Channel Backplane. Power down the console and remove Channels 15 and 16 as instructed in
Replacing Modules (on the following page). Locate the CPUA connector and re-seat, then reassemble the desk and
check the fault.
Again we will assume that in this instance this did not resolve the problem. This leaves three possible causes. The first is
that the channel backplane has developed a fault. The second is that one of the channel strips in Bay 2 has failed in such a
way as to corrupt the data on the Multidrop Bus. The third is that the CPU card has developed a fault with the hardware
that processes Multidrop Bus 2.
The first cause is highly unlikely. The channel backplane contains no active components, only copper tracks, and as such
can be discounted. The second cause is possible – to determine this, remove the channel strips from Bay 2, one by one,
ensuring you power down the console each time, and check the condition of the fault. If, after removing a module, the
remaining channel strips start to function, then you have located the problem. If you reach the last module and the fault
still occurs, don't forget to swap the remaining module with one of the others to ensure it is not the cause of the problem.
If the fault still persists then the cause must be the CPU. Once again, through a simple process of elimination, the cause
of the fault has been located.
Appendices Page A-14
AWS elta Owner's Manual