Alesis MMT-8/HR-16 blank screen with all lights on and unresponsive buttons fix скачать в хорошем качестве

Alesis MMT-8/HR-16 blank screen with all lights on and unresponsive buttons fix

I bought a broken Alesis MMT-8 from auction. When powering on, the screen is blank, all of the lights are on, and the buttons are unresponsive. Reports of this issue can be found online, but I couldn't find anyone who had found the cause, or fixed it. I found the schematic and service manual online, and began to troubleshoot. The service manual describes a reset circuit which is involved in the boot and power down functions of the CPU. Through understanding that circuit and its schematic I was able to identify the problem, and fix it. Initially I replaced 2 transistors, and a capacitor. Ultimately that led me to conclude that the LM339 comparator at U14 was most likely faulty.