The machine will not boot up. I have a green light on the soft power switch on the display. When switching soft switch to the emergency firmware mode I get the sleep mode button to light up a solid green. Other than that I have swapped the MFP/controller unit with a new one and the DC P/S PWB out of a working machine. I am getting off the chart readings on the Sub DC P/S PWB, DC P/S PWB, Mother PWB, Driver PWB and the PCU PWB. I am reading 240V DC out of all these boards, witch I know makes no scene it is a 20 amp 120V machine. I am at a loss and customer is down. Sharp tech support suggested the MFP witch I tried and it made no change.
I had a similar issue recently with a MX-7040 we changed HDD & sd card no help. It turned out to be an MFP Board. I know you have already tried that. One interesting note. I was getting double voltages so 24 showed 48 and other DC voltages did the same. I was a little puzzled.
Then I noticed that the meter I was using ( not my old meter ) but one that a newer tech uses had a very small sign wave on voltage selector and I thought it was on the straight line DC but was on AC. I guess I need new glasses.
try the mother pwb. The mfp and pcu boards plug into this board...as well as most of the fans switches etc. also try and remove the fuser and power it up with the right door open. Had one not power up once due to a short in the 120 line for the lamps in the fuser. Its possible that your meter is reading 24.0v which could be an accurate reading. You may also want to try a different set of roms.