Confirmed. 61-1 display, press self test button, get the chime, turn jackpot key, display blanks, site idle for about 3 secs, 61 comes up in display.
Guess I'm still not understanding something.....wouldn't the clear condition have been cleared by the presence of new board/CMOS, or would it be somehow retained in the GAME/REEL chips that were transferred to the new board? Also got the same condition when using the known good MPU from the RWB machine, with the RWB chips......and the 5x board worked fine in the RWB chassis.
Also, machine does have a cherry switch behind door for Bill Validator. all wiring there looks good as well.
Looks like you probably need to do the ram CLEAR process when you get your chips. After doing that you will need to set some settings on your machine, so to get ready for that it will be helpful if you read over the document for the SP chip in your machine. Can you post a photo of your mpu board showing the Game and Reel chips so we can read the label? That way the advice you get going forward will be specific to your SP chip.
While you have the mpu out of the machine it would be good to check the battery, measure it's voltage, see if it is getting old & weak, look for any sign of battery leakage. That's something that should be done on any machine when you first get it, can prevent having to do an mpu replacement because of battery damage.
To do the CLEAR procedure see the instructions in reply #4 above.
I don't know why exchanging the mpu with another good working mpu doesn't work. That's why I thought there could be a problem with the door optics or a security switch. But the display blinking and changing from 61-1 to 61 is the confirmation that your machine is stuck in the 61 loop problem, and only a CLEAR will fix that.
What could be going on is that the motherboard (the interconnect board that the mpu plugs into) has an eeprom chip. It holds certain security info about the machine. Perhaps it got corrupted and even with an mpu swap the machine still isn't able to initialize. Could be that the CLEAR chip not only clears the cmos ram on the mpu but it also restores the motherboard eeprom contents. just a guess, others more knowledgeable can help with this.