Hi recently acquired an Alesis S4 Plus module that was DOA – when powered on there was no display and just static from the outputs.
I have found and repaired 9 faults (broken traces / damaged vias), mostly between the FX ASIC / DRAM chip and output jacks. There’s no longer any noise from the outputs, and the display lights up, but it’s still not functional.
Symptoms are now:
- Display lights up with almost all segments lit (except channel numbers 1-8, the lines above those numbers, the 3 digits next to MIX, and the second line of character cells where A B C D and arrow usually show up).
- Am able to press Global and use Quad knob 1 to adjust the display contrast. (Contrast settings are saved, so the battery backup and SRAM are working at least somewhat)
- Am usually able to initiate the demo (hold down Global and press Mix or one of buttons 1-4). There’s no sound, but all display segments then light up. Sometimes need to power cycle the unit first.
I’ve double checked my fixes, checked for shorts etc, and also checked the EPROM contents against a ROM found online.
Any & all help greatly appreciated! Would be very interested in a schematic or service manual if one exists too