HP-25 - what could be wrong, simple question

[albertofenini]

Hi Everyone,
these are the waves captured from the unit under repair and a working one,
blue waves are from the working one, red waves from the broken one,
both were powered with an external pack of batteries, in RUN mode and displaying a 0.00
both have a good electrical connection between pin 11 of the ACT and pin 4 of the RAM
we don't know if the ram transplanted was working or not since it came from a broken unit

data wave (pin 11 of the ACT)
   


isa wave (pin 10 of the ACT)
   


FI2 wave (pin 16 of the ACT)
   


FI1 wave (pin 17 of the ACT)
   


SYNC (pin 22 of the ACT)
   


Any idea ??
Thanks for help !!