Front Panel Problems - Alesis Andromeda A6 Service Manual

3.3 Front Panel Problems

3.301 Buttons Don't Work or are Intermittent
° Make sure you have the latest version of the Front Panel Left PCB. If not, make sure all
of the ECNs are properly implemented. (Rev B of the board needs a 1000pF cap
soldered across pins 10 and 11 of U20).
° Make sure the diode that goes with the button is oriented correctly. If more than one
button doesn't work, there may be a problem with whole a row or column. See if the
failing buttons correspond to a row or column.
3.302 Knobs Jitter or Don't Reach Maximum Value or Don't Work
° Make sure the ribbon cable going from the Main board to the Front Panel Left board is
securely seated.
° Make sure the large 60-pin ribbon cable going across the Front Panel boards is properly
seated.
° Make sure the caps and resistors at the Main Mux (upper left corner of page 2 of the
Main PCB schematic) are the correct value and are properly soldered.
° Knob jitter can be caused by voltages exceeding 5V at the ADC mux input on the Main
board. Check the inputs to U21 on the Main board. If any voltages exceed 5V, find the
source (probably the tuning or temperature bus from the ASICs). One of the ASICs
might be bad. [ECN was written to remove R62 on Main PCB – make sure it was done].
° Swap Front Panels to see if the problem is with the Front Panel or Main Board.
° Make sure the unit has the latest software (V1.40.09 or later has new anti-jitter knob
code).
° Make sure the knob caps aren't pushed in so much that they're touching the front panel.
Pull the plastic cap slightly so that it is not sitting against the metal.
° Try looking at the muxed analog pot signal at the input of the pot ADC (page 2 of the
Main PCB schematic), U27 pin 1. The waveform should look like a "skyline", with each
"building" representing a pot level. If you turn all of the knobs down (to the left), the
waveform should be mostly flat, except for things like the pedal inputs, which are
normally high. If you see no signal here, it means the pot signal is not getting to the
ADC and therefore the micro.
3.303 LED Doesn't Work
° Make sure the LED is soldered and oriented correctly.
° If several LEDs don't work, the problem may be with a row or column in the LED
matrix. Check the row and column drivers.
3.304 Keys Don't Work
° Make sure the two ribbon cables going from the Main board to the Fatar keybed are not
being smashed by the Ribbon Controller bracket. Make sure the cables are routed
through the opening in the bracket. If the cables were damaged, replace them.
3.305 Ribbon Controller Doesn't Work
° Re-calibrate the ribbon by powering up while holding Soft Button 5. Make sure nothing
is touching the Ribbon Controller during this process.
° Go into diagnostic mode by holding down Soft Button 3 during power up. Verify ribbon
operation.
° Make sure the Ribbon Controller cable is plugged in properly.
Confidential Alesis Service Manual 8-31-0089-C