Whilst it is likely the PSU as per other posts, I found that when I changed the CMOS battery my MC200 similarly would not boot.

The solution was to boot the MC200 without the battery in place and then, very carefully, insert the new battery while the MC200 was still powered.

After this the MC200 worked normally and booted from cold just fine.

Worth a try.

808v6, M60, MC200, HD621, Lumagen XE, 504, SB Touch, 563, 201, 204, 208, MPMAX 221, M80, Explorer, Explorer2.