Thank you all for the warm welcome
Yes, I have a Digital-Volt-Meter and Logic-Tester available.
Just some background to my pcb in question.... The board is a sound card (C-19389) from a Gottlieb pinball System 1 manufactured 1980. I bought the pinball half a year ago without a working sound besides other issues.
The general optical condition of the pcb was quite good for my understanding. Due to my experience with other machine board of this age, I started to clean the board and replaced all electrolytic capacitors and potentiometer.
The circuit consist of a 6503 with a prom and a 6530. I read all over the web, that often times the 6530, which has an internal prom, looses the function. So I found a piggy back solution to replace the 6530 by a 6532 and an e2prom. Once done nothing happened. As I had a bit time pressure to make the game working for a bigger party I found the last 6503 on the market in our region. Again without success. Unfortunately I realised later, that the IC was installed in the wrong direction. No idea whether the 6503 IC survived the stupid action :-/ As I got angry in the meanwhile I put the pcb on side and board a repro with same form-fit-function. So far so good.
But to be honest I would make this original board working even if in the meanwhile lot of the electrical parts have been replaced. If somebody is interested in this, I have attached some pictures and the datasheet of the board.
When I read here thru the posts that I feel confirmed not to make the same approach again as I did... just replacement... better I have to go thru the scheme and try to varify what should be.
I will post my observation and ideas the next days/ weeks and if somebody has some helpfull comments in his mind....
Thank you so far!