Korg DDM-110 power issue

So, I got this one for cheap from a friend, after someone told him it could not be repaired. I cleaned the leahed battery terminals, resildered them, and for the last month tried to find the fault with my multimeter, oscilloscope, even AVR component tester. Everything seems to work, there is enough current everywhere, the only odd thing is 5V GOING TO the first row of batteries. That seems odd. I usually repair my gear myself, but but this one is too hard. I am ready to replace whatever, just point me in some direction. The service manual is easy to find online. Please help!