Enhanced MPU Issues

[Neonkiss]

I have an Enhanced MPU that will throw a Hopper over pay error when the handle is pulled. The issue is with the MPU as a replacement works fine. Has anyone had this before? do you know what component on the MPU causes this error?
 
Also have one that use to throw out the Netplex Link Down error until the machine warmed up. The issue was NOT with the power supply but caused by the MPU itself. It threw out one last error one day where it lost all accounting information. Turning the side key cleared and reset the machine only to have the MPU lock up on the Netplex Link Down error about an hour later. Now it dead and won't clear the error, has anyone seen this before?

[Retro tech repair]

Netplex Link Down error is very common things to try is the daughter board(flash or legacy adapter) green battery, but this has never fixed the problem of me i always have to replace the mpu. the hopper over pay when handle is pulled sounds like a problem with the SENET system. i would try replaceing the cabnet io board first as both systems go through that board. if it is deffenitally a problem on the mpu the SENET chip on the board is probably at fault.

[Neonkiss]

I have an Enhanced MPU that will throw a Hopper over pay error when the handle is pulled. The issue is with the MPU as a replacement works fine. Has anyone had this before? do you know what component on the MPU causes this error?
 

This problem was solved by replacing the I/O board next to the MPU. The replacement MPU that worked was a 75512702 and will work with the black plastic I/O boards 14940200. These I/O will throw the error above if used with MPU 75512701
 
The third picture shows the 75512702 MPU and is easily identified by the missing components on the corner of the board.