wise65vw wrote: I don't mean to be condescending, but is there a chance the diode was put in backwards? Just a thought.
Dr. Optigan wrote: Yeah, I definitely see the similarities. Any idea about the history of this design? Guessing TI had a hand in it, given the diagram in post 7, but the differences make me wonder.
Ty_Eeberfest wrote: Are all - and I mean ALL - unused reset pins on the 7490s and 7492s tied down to ground? They should be. A floating reset pin is prone to all kinds of randomness.
Ty_Eeberfest wrote: I will keep repeating this until you acknowledge it and hopefully do it: All this discussion is moot until you not only clean the board but inspect all solder joints under magnification and reflow as needed.