Hi to everybody,
My Bally Eight Ball deluxe is finally ready and in great condition after a time consuming restoration. The only problem remaining is a missing light from the right Thumber bumber.
I tested continuity from the socket to the transistor Q13 and Decoder and it is Ok.Transistor also tested ok.
I further checked the MC14028B decoder and i found that there is ground in pin 6 ,related to this light so i said...great. I have found the problem and it was an easy fix.....
It was not that easy! I replaced MC14028 with an alternative decoder HEF 4028BP that said to be the same. I fixed the Light on right thumber bumber but then the 30K Left Lane light stays always on.
In testing mode i also noticed that after a while the first E from deluxe starts staying on .
Ok, next step to remove this decoder and put the initial one. Same behavior as in the beginning.Strange!!!!
Then i assumed that HEF 4028BP may not be the proper decoder and i tried to find a CD4028 that already has been replaced long ago on the board and works fine. Same behavior. Always on the 30 K Left Lane and after a while the same for first E.
I don't understand this behavior.
I will appreciate if someone has a suggestion. Anything will be much appreciated.

Iordanis

Auxilary Board (resized).jpg

Thank you @yeoldpinplayer. It is true that Pinwiki is like a bible! First thing to check!
But i have checked all connentions and arefine.
As told when i have the initial Decoder i miss bumber light . When replace with new i have constant lighting in 30K and after a while another one .All related with the same Decoder. It makes no sense!

Yes, i can remove the decoders and put a socket. But all problems are located in U3 decoder which i have already a socket installed and i change between new ones.

Problem Solved....
I reseated J4 Connector of MPU .Now all lights are fine!
Never trust old connections.
Thank you YeOldPinPlayer & Rikoshay for your suggestions and help.