The WDC processor has bus-enable (BE) on pin 36 which needs to be high. Does your board pull it down? Pin 36 was NC on previous 65c02's. The WDC processor has a very weak internal pull-up on 36, so weak that contamination on the board could be pulling it down.

Hello,

thank you so much, you ...

Hello,

I have a broken chess computer running on a Ricoh RP65C02G. I replaced the CPU with another of exactly the same type, and it worked.
So I've ordered some spare CPUs of the type WDC65C02S6TPG-14, and all 3 of them don't work. Did I miss any compatibility items there?

Thanks for any help ...