Troubleshoot a main board of Akai MPC Live (with Rockchip RK3288 microprocessor) - Page 1
Forum section: electronics / repair

author: klokan
author_rank: Newbie
timestamp: November 23, 2024, 12:39:23 pm
content: Hi guys,I'm new to the forum and i'm looking for some help. I have a broken MPC Live MK1 that I'm trying to fix. When I try to turn it on, pads light up for a few seconds and then it shuts off. When connected to a power brick, battery charges and holds charge as expected. Unit behaves in the same way as the one shown in the video on below page:https://www.reddit.com/r/mpcusers/comments/yfuqdy/mpc_live_wont_turn_on_can_anyone_help_me_find_out/I've taken the whole thing apart and looked for some obvious faults, like blown components, but couldn't find any. I'm by no means an expert in electronics, but I also did a continuity test on diodes, caps etc. and couldn't find any shorts.There's not much available about this issue online, except below post on this forum, where someone was troubleshooting the same board with similar issues from another product:https://www.eevblog.com/forum/repair/trying-to-troubleshoot-a-main-board-with-rockchip-rk3288-microprocessorSomeone there suggested connecting the board to a computer via UART port and configuring it to 115200 baud, 8 bits, no parity, 1 stop bit and no handshake, so that's what I did, but board basically didn't return anything, except for a few jibberish characters from time to time (pushing the reset button would generate such stuff every time). I thought that maybe the baud rate is incorrect, but I also tested my friends MPC Live with the same settings and it worked just fine and printed out the whole boot process, so settings are definitely correct. So, the board doesn't start booting at all - there's something preventing it from starting that process, I guess.Forgot to mention that I also tried holding down the Recovery button when powering on, but that didn't change anything. Board does not go into update mode and is not seen by the computer.Also, two LEDs marked as LED STATE 1 and LED STATE 2 are not lighting up under any circumstance. CR1220 battery that's attached to the board was dead when I got it, but I replaced it with a brand new one.There are some voltages written on the board where there's space for more LEDs, so I checked those as well (not because I knew what I was doing, but to see if measurements will match what's writen).There's a close up shot of that section of the board, and results attached. There are discrepancies on three points, and voltages are present for a short period of time when power button is pressed. When it shuts down, there's no voltage on those points.I'm hoping that someone here can point me in the right direction based on the details provided, or suggest other things I could test. I'd really like to fix this oneThanks in advance!

author: coromonadalix
author_rank: Super Contributor
timestamp: November 24, 2024, 12:04:22 am
content: some leds voltages are bad because the led is not there, you do see some resistors going to them, but led not installednormally yes the recovery should put the board in some bootloader modeyou have rockchip toolsin some cases : to be seen you need to install the adb drivers 1st, even if the rk chip is in boot loader, it could or would not be seen in windows, and the rk tools would see it and show you if it is accessible or not, and see all the boot files / contentit could be some flash failure ??have you read the linked thread ... ?

author: klokan
author_rank: Newbie
timestamp: November 24, 2024, 12:49:03 pm
content: Hi coromonadalix and thanks for answering!I didn't know about Rockchip tools, thanks for bringing that up. Will give them a go as soon as I get the chance, but I have a feeling problem lies elsewhere because board shuts down after a few seconds even when trying to boot in Recovery mode.And thanks for explaining the cause of difference between expected and measured voltage.Not sure if it's a flash failure, because unit was faulty when I received it and I don't know what previous owners have done to it.I read the linked thread, and someone there mentioned measuring the output voltages of each of the switchmode supplies and LDO regulators. But, I don't know how to locate measurement points on the board nor what voltages should I expect to find.Same user also said that PMIC is programmed to power up each supply in a predefined order, so the uP might get hung up if each supply doesn't come up at the right time. That seems like a reasonable guess, but I wouldn't know how to inspect that. Would changing the IC with a brand new one (the exact same model) fix things? PMIC is probably a chip marked as ACTIVE 8846Q JG217 on the board, right?