jasonsbeer
commented
11 months ago Does the keyboard reset work? If not, there may be issues with U805 or associated passives. The reset switch works by pulling pin 1 of XU1 to ground. This also pulls pin 10 of U805 to ground. XU1 will then hold pin 1 low for 150ns after the reset button is released.
Placing your finger on an IC can create just enough pressure to "fix" a floating leg. If you have a floating leg, it can be hard to check continuity because placing a probe on the leg can bend it just enough to work. I would start by reflowing U805, XU1, and associated passives.
Hi! Finally I finished assembling the a2000 and it started up almost immediately! :) But as it turned out, the reset practically doesn’t work... every third or tenth time, or even the twentieth time, it works... I can’t understand the reason? When inspecting the reset generation circuit, the following was noticed - if you put your finger on the side 8-9-10-11 of the U805 leg and press the reset button, then the reset works well; removing the finger also starts to work poorly... I measured the esr of capacitors C813 C814, everything is fine normal... where to look?