Alesis Fusion 6HD, Service Manual

Page: 212 / 216

Confidential Alesis Service Manual 8-31-0167-A
11. Troubleshooting Guide
This guide is an attempt to help the service technician make productive use of
the information provided by the tests in Diagnostic Mode.
As noted elsewhere,
some Diagnostic Mode tests are destructive to user data, so care should be
taken when choosing which tests to run.
The notes below are organized by
the Diagnostic Mode page to which they apply. This section is currently rather
sparse, and will be expanded based on feedback from service centers. If you
would like to contribute something to this section, please contact Alesis.
11.1. UI
11.1.1. LEDs
For individual LEDs that are dim or completely off, check solder joints at the
LED, check PCB signal trace continuity between the LED and the LED row
current limiting resistors (47-ohm and 15-ohm) and between the LED and the
LED/switch column transistors, and replace LED if necessary.
For large numbers of LEDs that are dim or completely off, check if the LEDs
correspond to the same row/column, and check the appropriate row or
column transistors, resistors, and buffers. Check solder joints, PCB trace
continuity, and components.
11.1.2. Switches
See “ LEDs ” section above.
11.1.3. Keys
Half or completely non-functional: check the 2 cables between main PCB and
keybed for a good connection, and that cables are not damaged
If there is a group of consecutive keys that are failing, one or more "columns"
of the switch/key matrix probably have problems. Concentrate on the nets
named KBD_COL00 through KBD_COL21 on the Main PCB. Check the
solder joints at connectors J18, J19, and J22 (depending on model) and at
resistor arrays R104, R105, R106, R107, R110, and R111. Also check the
cable connector pins and wires corresponding to these nets. If none of these
seem to be at fault, the BGA solder connection(s) of the FPGA U25 may be
at fault, which requires replacing the PCB.
If there are a bunch of failing keys spread out relatively evenly across the
keybed, one or more "rows" of the switch/key matrix probably have problem.
Concentrate on the nets named KBD_ROW0 through KBD_ROW7 on the
Main PCB, and on the associated cable connector pins and cable wires.
Specifically, check the connections on the pull-up resistor arrays R119 and
R120. If none of these seem to be at fault, the BGA solder connection(s) of
the FPGA U25 may be at fault, which requires replacing the PCB.
11.2. I/O
11.2.1. Power
This test is for engineering purposes only and has no value to service
technicians.