Chosen Solution
Hello! I have a Korg Volca Sample MIDI Controller Keyboard that is not powering on. I can measure with my DMM the 9V at the cables coming from the batteries connecting to the PCB. The power switch is good and tested with continuity mode and resistance meter. https://imgur.com/a/FZTSx1i What I found out is, that after the first Fuse (see second picture FU1 yellow) there is no 9V. Before the fuse there is 9V. So i guess the fuse is dead.
The second thing is, that the voltage controller TPS62112 is shorted to ground on its pins 1 and 2 which are the VINs for it. Is it possible that the chip is dead too? This is also a pictures where the two VINs pins are connected to a capacitor https://imgur.com/a/XLGEz5n Would it be a good approach to replace that “M” Fuse (I guess it is 4A???) and the TPS62112 to see if everything works? Some of those ceramic caps around the chip beep from both sides to ground. Not sure how to find out if those are ok too.
Hi @mike8 , I was hoping for a model number so that perhaps a schematic could be found. Regarding the IC TPS62112 it looks like it is faulty. Here’s the pinout for the chip that shows the pin 1 is PGND and pin 2 is VIN. The datasheet (click on the diagram to enlarge) shows a P-Channel and a N-Channel power MOSFET is connected between 1 & 2. Although you may have to test it out of circuit to really prove whether the there is a short circuit between the two or if it is somewhere else on the board. Testing capacitors still on a board may not give accurate results. You need to lift one end off the board and then test. Usually though ceramic capacitors are fairly robust but have had a case of where one was always operating at the top end of its’ working voltage value and it failed eventually so maybe it is always good to test to make sure. Sorry that I can’t be of more help on this one. Update (05/07/2020) Hi @mike8 , If the circuit is the same or similar you will not only need to check the IC but the board as well to check if there is a short circuit from the regulator’s output to earth (or ground), which has caused excess current to flow through the regulator damaging it. Here’s an image taken from the link you provided that shows where to test. You need to remove the IC from the board and check if it is still short circuit between pins 1 & 2 as it still may have been IC component failure and not a problem elsewhere in the circuit that caused it to fail. If the IC tests OK in that there is no short circuit between pins 1 & 2 but there is on pins 1 & 2 on the board position for the IC then it becomes a matter of isolating it to where it is. This would involve removing components from the board until it was found where there was a short circuit. In the case of 1 & 2 test between pin 2 on the board and earth If the IC tests short circuit between pins 1 & 2 and not the board on pins 1 & 2, then you would also need to test between IC pins 1 & 15 on the board to make sure that there was no short circuit between the +5V voltage rail and earth i.e. pin 15 and earth, which would have damaged the IC. This will be more involved. The arrow shows where the output from the regulator is which powers the circuit.
(click on image to enlarge for better viewing)
