DekatronNixie wrote: Hi,
Having looked at your photo with the components I suggest that you check pin number 4 and 12 of the 7490 (stamped with date code 7227) as the strip sockets used there seems to be "open" more than the other pins. You can lift the ic's out of their sockets and very gently push these sockets closed again, but don't press to hard as it will be problematic to put the ic's back again.
While you are at it you should check each and every ic socket and in your case it might help to just remove the ic's and put them back, the corossion that can build up over the years in these sockets can be part of the problem.
I would also replace the red drop formed tantalum capacitor as those are known to short and burn when they get old. I have replaced hundreds of those, most before they have exploded but a lot after they have exploded and then I had to replace components close to them and clean the PCB's. It looks like it says "10" and "25V" on yours, then it is 10uF/25V.