Turning on the equipment, you should see a MLO/U-boot prompt, which will follow a sequence of operations with diagnostic messages. In this case, I would try to find three pins that would correspond to a UART port (maybe marked on the silk as TX, RX and GND) and connect a serial cable to a terminal program on a computer, configuring it to 115200 baud, 8 bits, no parity, 1 stop bit and no handshake (these are the most common settings for such ports in the marketplace). At this moment I am using the old mainboard with nothing else attached (buttons etc) only the 12V power supply. Any tips/help troubleshooting this would be greatly appreciated. Just trying to 'solidly' figure out what the issue could be, even though I am not able to fix it. Not having the schematic makes it that much harder. I am quite new to troubleshooting circuits including microprocessors. If I press and hold this button, the voltage tends to remain at the pins for as long as I hold it. The button used to turn on the unit is one of those momentary push buttons which I assume fires some kind of an interrupt. The nPBSTAT is used to fire an interrupt and it seems to be doing that as well. Start up sequence seems to work I even get 5V at the PWRHLD pin for a moment and it goes back to 0V. Going through the datasheet for the ACT8846 I found out that there was a way to manually reset the processor by shorting nPBIN to ground. I tried to find any obviously faulty components, couldn't find it. So as I said the microprocessor used Rockchip RK3288, the power management IC used is the ACT8846.
So I thought I will just mess with just for my personal reference. The guitarist it not really interested in reviving it anymore. This time however I was not able to get it back to life with the reset button. This time I was able to get it back to life by pressing the reset button, after couple of months it strikes again. Installing the new board rectified the problem, but after about three weeks the same thing happened. However I was able to source a spare board from the party which manufactures the main board. The manufacture seems to not acknowledge this known issue and weren't very helpful. Nothing seems to get the unit to start back up - resetting etc. Doing an internet search showed that a lot of people was going though the same situation. The main board is made up of Rockchip RK3288. The unit does not boot up, goes through a start up sequence and just turns off. Hi there everybody, Sometime back I received a faulty guitar effects pedal board, it quite famous among the guitarist apparently.
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