Imoortant
Due to the complexity of the modules involved, it is often difficult to determine which module is at fault when
a communications problem occurs.
KEYPAD/DISPLAY BOARD
DATA DATA CLOCK
IN
OUT OUT
I
24 PIN DISPLAY
/
1
I
DIGITAL BOARD
DATA DATA
IN
OUT
I
ASYNCHRONOUS
PORT
CABLE
DATA
DATA CLOCK
Figure 7
-
Communications Path
If a communication problem occurs (i.e., no display or no response to button presses or keys), it could be
something as simple as a bad cable, or it could be a problem in one of the modules. To help you identify a
faulty module, a Communication Test Board is available from ENSONIQ Customer Service*. The
Communication Test Board simulates the operation of the keyboard and can be used as a “known good”
module in place of the keyboard for troubleshooting.
*This is the same communications test board that was sent out to service centers in 1990 to troubleshoot
polypressure keyboard problems.
--
IMPORTANT!
When using the Communication Test Board, keep in mind that it is sensitive to static discharge. Handle the
board by the edges and store it in the anti-static shipping bag when not in use. Do not let the board short out
when testing, place an insulator (cardboard, paper, etc.) underneath it,
Attaching the Communications Test Board
If an ASR has a communications problem, turn the unit off and unplug the 20-pin keyboard ribbon cable from
the digital board at connector J7. Plug the 20-pin ribbon cable from the Communication Test Board into
57.
This will eliminate the keyboard as a variable. Turn the system on. If the communications problem persists,
you know the keyboard is not at fault. If communication is restarted, however, the keyboard is at fault.
--
There is one further complication. Since the communications path between the keyboard and keypad/display
board is routed through the digital board, there is a remote possibility that the printed circuit connections
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10
ASR Service Manual
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