Hi hope everyone is doing well! I have a issue with my Zaxxon arcade: I just replaced crt with a tv donate. which has worked out just fine. my issue is ram 1 no good! I checked u70 & u71 I have 5v at both on pin 18. before I replace anything else I should check? there are no capacitors in the area just disc ones which I will check next. I have a logic probe tester but not sure which pins I should try is there any where on this site I can get a idea to see if a signal I'm suppose to have? thanks guys in info or direction would be appreciated.