My junk yard has no sound and no display. Problem is narrowed down to the MPU board.
questions about the security chip:

1. What are the possibilities to check or the security chip on the MPU board is working properly?
2. Is it possible that a defective security chip results in a non-working AV board?

I ask these questions because something on the MPU blocks the AV board. This was also the case when the JY MPU was tested in another wpc 95 pinball machine (SS).

MPU starts up as it should but there must be a bug.
AV board from the JY works fine in the SS. Since the SS is not my machine I can not check the epron with security chip in the SS because I am afraid for damage. I have no other wpc 95 machine with security chip to see if the MPU starts up like it should.

The following parts on the MPU are replaced without solving the problem:
U1, U2, U3, processor U4, U5, Ram U8, ASIC U9, U21
eprom G11.

All diodes and resistors were checked and ok

Please hep!