Eventide H3000
This time, true royalty landed on my workbench: an Eventide H3000 effects processor. The problem with this unit was a complete failure to boot and a system lock-up. The only sign of life was the backlit LCD with its first line filled with █ characters and absolutely no response from the front panel controls.
After verifying that all supply voltages were present, suspicion fell on the reset circuit of the Motorola 68A09 main processor, which quickly proved to be the right diagnosis. Failure to initialize alphanumeric displays is almost always caused by the processor responsible for communicating with the display module not running properly, and therefore failing to initialize it (let alone send any display data). As so often, the culprit turned out to be a failed electrolytic capacitor in the reset circuit of a dedicated IC.
I also have to give credit to the designers of this unit —it’s an impressively complex digital system built around several microprocessors.
